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  • 1.
    Alay-e-Abbas, Syed Muhammad
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Pakistan.
    Abbas, Ghulam
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Zulfiqar, Waqas
    Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Pakistan; Department of Energy Conversion and Storage, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark.
    Sajjad, Muhammad
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Physics, Khalifa University of Science and Technology, Abu Dhabi, 127788, United Arab Emirates.
    Singh, Nirpendra
    Department of Physics, Khalifa University of Science and Technology, Abu Dhabi, 127788, United Arab Emirates; Center for Catalysis and Separation (CeCaS), Khalifa University of Science and Technology, Abu Dhabi, 127788, United Arab Emirates.
    Larsson, J. Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Structure inversion asymmetry enhanced electronic structure and electrical transport in 2D A3SnO (A = Ca, Sr, and Ba) anti-perovskite monolayers2023In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 16, no 1, p. 1779-1791Article in journal (Refereed)
    Abstract [en]

    Anti-perovskites A3SnO (A = Ca, Sr, and Ba) are an important class of materials due to the emergence of Dirac cones and tiny mass gaps in their band structures originating from an intricate interplay of crystal symmetry, spin-orbit coupling, and band overlap. This provides an exciting playground for modulating their electronic properties in the two-dimensional (2D) limit. Herein, we employ first-principles density functional theory (DFT) calculations by combining dispersion-corrected SCAN + rVV10 and mBJ functionals for a comprehensive side-by-side comparison of the structural, thermodynamic, dynamical, mechanical, electronic, and thermoelectric properties of bulk and monolayer (one unit cell thick) A3SnO anti-perovskites. Our results show that 2D monolayers derived from bulk A3SnO anti-perovskites are structurally and energetically stable. Moreover, Rashba-type splitting in the electronic structure of Ca3SnO and Sr3SnO monolayers is observed owing to strong spin-orbit coupling and inversion asymmetry. On the other hand, monolayer Ba3SnO exhibits Dirac cone at the high-symmetry Γ point due to the domination of band overlap. Based on the predicted electronic transport properties, it is shown that inversion asymmetry plays an essential character such that the monolayers Ca3SnO and Sr3SnO outperform thermoelectric performance of their bulk counterparts.

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  • 2.
    Blomqvist, Anton
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Developing a Mathematical Model of a Nuclear Thermal Rocket Engine2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Renewed enthusiasm for space exploration brings more ambitious missions to light butthe constraints of chemical rockets put imposing limits on what is feasible. Nuclearthermal rockets provide an attractive and efficient alternative to shorten travel timesand increase payload. In this thesis, a dynamic model of a Nuclear thermal rocketengine is derived in order to simulate the resulting performance of the engine. Thework is inspired by a similar model on the Space Shuttle Main Engine (SSME).

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  • 3.
    Castellanos, Leonardo
    et al.
    Ultrafast Laser Diagnostics and Flames Laboratory, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, Delft 2629 HS, the Netherlands.
    Mazza, Francesco
    Ultrafast Laser Diagnostics and Flames Laboratory, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, Delft 2629 HS, the Netherlands.
    Bohlin, Alexis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Ultrafast Laser Diagnostics and Flames Laboratory, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, Delft 2629 HS, the Netherlands.
    Water vapor in hydrogen flames measured by time-resolved collisional dephasing of the pure-rotational N2 CARS signal2023In: Proceedings of the Combustion Institute, ISSN 1540-7489, E-ISSN 1873-2704, Vol. 39, no 1, p. 1279-1287Article in journal (Refereed)
    Abstract [en]

    We present a novel diagnostic technique to probe water vapor (H2O) concentration in hydrogen (H2) combustion environments via the time-resolved measurement of the collisional dephasing of the pure-rotational coherent anti-Stokes Raman scattering (CARS) signal of nitrogen (N2). The rotational Raman coherence of the N2 molecules, induced by the interaction with the pump and Stokes laser fields, dephases on a timescale of hundreds of picoseconds (ps), mostly due to inelastic collisions with other molecules in atmospheric flames. In the spatial region of H2 flames where H2O is present in appreciable amount, it introduces a faster dephasing of the N2 coherence than the other major combustion species do: we use time-resolved femtosecond/picosecond (fs/ps) CARS to deduce the H2O mole fraction from the dephasing effect of its inelastic collisions with N2. The proof-of-principle is demonstrated in a laminar H2/air diffusion flame, performing sequential measurements of the collisional dephasing of the N2 CARS signal up to 360 ps. We measure the temperature and the relative O2/N2 and H2/N2 concentrations at a short probe delay, and input the results in the time-domain model to extract the H2O mole fraction from the signal decay, thus measuring the whole scalar flow fields across the flame front. We furthermore present single-shot simultaneous thermometry and absolute concentration measurements in the turbulent TU Darmstadt/DLR Stuttgart canonical ‘H3 flame’ performed by dual-probe CARS measurements obtained with a polarization separation approach. This allows us to probe the molecular coherence simultaneously at ∼20 and ∼250 ps on the basis of a single-laser-shot, and record the resulting signals in two distinct detection channels of our unique polarization-sensitive coherent imaging spectrometer. The proposed technique allows for measuring the absolute concentrations of all the major species of H2 flames, thus providing a full characterization of the flow composition, as well as of the temperature field.

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  • 4.
    Da Silva, Adrien
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Frostevarg, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kaplan, Alexander F.H.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The influence of laser-induced recoil pressure on particles speed in Directed Energy Deposition2022In: 12th CIRP Conference on Photonic Technologies [LANE 2022] / [ed] M. Schmidt, F. Vollertsen, B.M. Colosimo, Elsevier, 2022, Vol. 111, p. 381-384Conference paper (Refereed)
    Abstract [en]

    Directed Energy Deposition is a common Additive Manufacturing technique used for its high deposition rate, but the interactions between the powder stream and the laser beam are still not completely understood. It is known that the powder particles heat up in the laser beam and some theoretical models predict that they can reach vaporization temperature and are significantly accelerated by the recoil pressure. In order to learn more about these phenomena, AlSi10Mg powder streams were observed with a high-speed camera at different laser powers and a particle-tracking software was used to measure the speed of the particles. The results show no significant increase of particle speed near the powder focus where the powder is processed, nor further below the powder focus. The high initial speed of the particles results in a short travelling time through the laser beam and in a very small effect of the recoil pressure.

  • 5.
    Dahir Ahmed, Ibtisam
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Improving the experimental setup for ultrasound-optical tomography imaging2023Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    According to Bröstcancer förbundet, mammography is not efficient at detecting tumors in dense breast tissue or diagnosing breast cancer at its early stages. Ultrasound-optical tomography (UOT) is an imaging technique in development and has the potential for deep-tissue imaging. If ultrasound-optical tomography were implemented, it would be easier to differentiate between malignant, benign, and healthy tissue from any type of breast tissue.

    UOT is an imaging technique that takes advantage of high penetration depth and high spatial resolution of ultrasound imaging and optical imaging. In UOT, a laser light and an ultrasound pulse propagate through the tissue simultaneously at a frequency f$_L$ and f$_{US}$, respectively. The light will scatter while it propagates through the tissue and some of this scattered light will become frequency shifted by ultrasound pulse due to the acousto-optic effect. The tagged light will have the frequency $f_T = f_L + f_{US}$. The tagged (frequency shifted) light can be separated from the untagged light (unshifted light) using a thulium-doped lithium niobate, Tm$^{3+}$:$~$LiNbO$_3$, crystal as a filter. The crystal is kept at a temperature close to zero kelvin because then it exhibits unique characteristics, e.g. it has a narrow linewidth and long-lived hyperfine levels at this temperature. The filter is created by a method known as spectral hole burning (SHB). A laser beam is used to transfer electrons from the ground state to the excited state to create a hole at a specific wavelength. The spectral hole is created at the frequency of the tagged light and hence a narrow bandpass filter is constructed inside the crystal. The tagged light is fully transmitted through the filter while it highly attenuates untagged light. The tagged light is detected with a photodiode and processed in MATLAB after it has been transferred to an oscilloscope.

    This thesis aims to model and design a phantom probe that minimizes vibration and other unwanted movements or disturbances during measurements. The automated phantom holder will be used for the recording of 3D images. Another task of the thesis was to obtain the absorption spectrum of a 0.005$\%$ Tm$^{3+}$:$~$LiNbO$_3$ crystal when it is cooled down to 3$~$K to ensure that the crystal has the same absorption characteristics as predicted in literature. The absorption line at $\sim$ 800$~$nm is of interest since oxyhemoglobin and deoxyhemoglobin have similar absorption coefficients at $\sim$ 800$~$nm. Optical absorption and scattering information will help determine if the sample contains a cancerous region.

    The phantom probe was modeled in Solid Works and manufactured through 3D printing. In this setup, the sample holder was chosen to be translated while the ultrasound transducer was stationary to generate less blurry images. The design of the probe has to accommodate two detection schemes, reflection and transmission mode. The phantom probe was automated using a linear servo actuator since it was controlled with pulse-width modulation (PWM). It used a square signal as an input that could be generated with an Arbitrary signal generator (AWG). Using a device that operates with a signal was important because it would make it easier to integrate it into the experimental setup. The whole phantom probe was constructed in a cost-efficient way and in a way that it could be easily incorporated into the experimental setup.

    The absorption spectrum showed that the crystal has an absorption line at $\sim$ 794.3$~$nm. This absorption spectrum was compared to an absorption spectrum taken at 8$~$K on the same crystal and captured with a different method. Both absorption spectra had the same absorption peaks at almost the same wavelengths but they also showed few discrepancies that may depend on the temperature difference and the recording method. In this thesis, the absorption spectrum data taken was captured by sweeping the wavelength. The signal was captured with a photodiode, transferred to an oscilloscope, and then processed in MATLAB. The absorption spectrum data at 8$~$K was obtained using a Fourier transform spectrometer, resulting in data with little noise and well resolved peaks.

    To conclude, a functional and robust phantom probe was designed and manufactured that could withstand vibration and other undesired movements. An absorption spectrum of Tm$^{3+}$:$~$LiNbO$_3$ crystal was obtained at 3$~$K and compared to absorption taken at 8$~$K and compared to literature and previous measurements under similar conditions.

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  • 6.
    Dembele, Vamara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Wahl, Joel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ramser, Kerstin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Correlation properties of a spatially quasi-incoherent imaging interferometer2022In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 61, no 19, p. 5806-5812Article in journal (Refereed)
    Abstract [en]

    The depth-gating capacity of a spatially quasi-incoherent imaging interferometer is investigated in relation to the 3D correlation properties of diffraction field laser speckles. The system exploits a phase-stepped imaging Michelson-type interferometer in which spatially quasi-incoherent illumination is generated by passing an unexpanded laser beam through a rotating diffuser. Numerical simulations and optical experiments both verify that the depth-gating capacity of the imaging interferometer scales as 𝜆/2NA2𝑝λ/2NAp2, where 𝜆λ is the wavelength of the laser and NA𝑝NAp is the numerical aperture of the illumination. For a set depth gate of 150 µm, the depth-gating capacity of the interferometer is demonstrated by scanning a standard USAF target through the measurement volume. The results obtained show that an imaging tool of this kind is expected to provide useful capabilities for imaging through disturbing media and where a single wavelength is required.

  • 7.
    Dobryden, Illia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Division of Surface and Corrosion Science, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Drottning Kristinas väg 51, SE-100 44, Stockholm, Sweden.
    Korolkov, Vladimir V.
    Park Systems UK Limited, MediCity Nottingham, Thane Road, NG90 6BH, Nottingham, UK.
    Lemaur, Vincent
    Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000, Mons, Belgium.
    Waldrip, Matthew
    Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, NC, 27109, USA.
    Un, Hio-Ieng
    Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK.
    Simatos, Dimitrios
    Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK.
    Spalek, Leszek J.
    Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK.
    Jurchescu, Oana D.
    Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, NC, 27109, USA.
    Olivier, Yoann
    Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, Université de Namur, Rue de Bruxelles, 61, B-5000, Namur, Belgium.
    Claesson, Per M.
    Division of Surface and Corrosion Science, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Drottning Kristinas väg 51, SE-100 44, Stockholm, Sweden.
    Venkateshvaran, Deepak
    Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK.
    Dynamic self-stabilization in the electronic and nanomechanical properties of an organic polymer semiconductor2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 3076Article in journal (Refereed)
    Abstract [en]

    The field of organic electronics has profited from the discovery of new conjugated semiconducting polymers that have molecular backbones which exhibit resilience to conformational fluctuations, accompanied by charge carrier mobilities that routinely cross the 1 cm2/Vs benchmark. One such polymer is indacenodithiophene-co-benzothiadiazole. Previously understood to be lacking in microstructural order, we show here direct evidence of nanosized domains of high order in its thin films. We also demonstrate that its device-based high-performance electrical and thermoelectric properties are not intrinsic but undergo rapid stabilization following a burst of ambient air exposure. The polymer’s nanomechanical properties equilibrate on longer timescales owing to an orthogonal mechanism; the gradual sweating-out of residual low molecular weight solvent molecules from its surface. We snapshot the quasistatic temporal evolution of the electrical, thermoelectric and nanomechanical properties of this prototypical organic semiconductor and investigate the subtleties which play on competing timescales. Our study documents the untold and often overlooked story of a polymer device’s dynamic evolution toward stability.

  • 8.
    Dominguez, Armand
    et al.
    Lund University, Div. of Combustion Physics, Box 113, 221 00 Lund, Sweden.
    Borggren, Jesper
    Beamonics AB, Tellusgatan 13, 224 57 Lund, Sweden.
    Xu, Can
    Beamonics AB, Tellusgatan 13, 224 57 Lund, Sweden.
    Otxoterena, Paul
    RISE Research Institutes of Sweden, Box 857, 501 15 Borås, Sweden.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. RISE Research Institutes of Sweden, Box 857, 501 15 Borås, Sweden.
    Leffler, Tomas
    Vattenfall AB, Laboratorievägen, 814 26 Älvkarleby, Sweden; Chalmers, Chemistry and Chemical Engineering, 412 96 Göteborg, Sweden.
    Bood, Joakim
    Lund University, Div. of Combustion Physics, Box 113, 221 00 Lund, Sweden.
    A compact Scheimpflug lidar imaging instrument for industrial diagnostics of flames2023In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 34, no 7, article id 075901Article in journal (Refereed)
    Abstract [en]

    Scheimpflug lidar is a compact alternative to traditional lidar setups. With Scheimpflug lidar it is possible to make continuous range-resolved measurements. In this study we investigate the feasibility of a Scheimpflug lidar instrument for remote sensing in pool flames, which are characterized by strong particle scattering, large temperature gradients, and substantial fluctuations in particle distribution due to turbulence. An extinction coefficient can be extracted using the information about the transmitted laser power and the spatial extent of the flame. The transmitted laser power is manifested by the intensity of the 'echo' from a hard-target termination of the beam located behind the flame, while the information of the spatial extent of the flame along the laser beam is provided by the range-resolved scattering signal. Measurements were performed in heptane and diesel flames, respectively.

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  • 9.
    Enrichi, Francesco
    et al.
    Department of Computer Science, University of Verona, Ca' Vignal 2, Strada Le Grazie 15, 37134 Verona, Italy; CNR-ISP Institute of Polar Sciences, Via Torino 155, 30172 Mestre, Venezia, Italy.
    Cassetta, Michele
    Department of Computer Science, University of Verona, Ca' Vignal 2, Strada Le Grazie 15, 37134 Verona, Italy.
    Daldosso, Nicola
    Department of Computer Science, University of Verona, Ca' Vignal 2, Strada Le Grazie 15, 37134 Verona, Italy.
    Cattaruzza, Elti
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172, Venezia-Mestre, Italy.
    Riello, Pietro
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172, Venezia-Mestre, Italy.
    Zairov, Rustem
    Aleksander Butlerov Institute of Chemistry, Kazan Federal University, Kazan, 420008, 1/29 Lobachevskogo str., Russian Federation.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172, Venezia-Mestre, Italy.
    Righini, Giancarlo C.
    CNR-IFAC Nello Carrara Institute of Applied Physics, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy.
    Effect of the crystal structure on the optical properties and Ag sensitization of Tb3+/Yb3+ ions in silica-zirconia glasses and glass-ceramics2022In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 49, no 24 Part BArticle in journal (Refereed)
    Abstract [en]

    The role of the material structure in the energy transfer between Ag and Tb3+/Yb3+ ions is studied in silica-soda-zirconia sol-gel glasses and glass-ceramics. The preparation of Tb3+ and Yb3+ doped silica-soda-zirconia layers was carried out by sol-gel and dip-coating, followed by thermal annealing. The precipitation of zirconia nanocrystals was obtained by controlling the annealing temperature: from a full amorphous glass at 700 °C into a glass-ceramic at 1000 °C. A different crystalline structure of zirconia nanocrystals, tetragonal or cubic, was controlled by the rare-earth doping and investigated in relation to the Tb3+/Yb3+ optical properties. Moreover, Ag codoping was introduced by ion-exchange, obtaining a significant photoluminescence enhancement, both in the intensity and in the broadness of the excitation band, covering the whole UV region and part of the violet-blue region. Ag-sensitized Tb3+/Yb3+ doped silica-soda-zirconia glass-ceramics were attested to be potential candidates for energy-related applications, such as spectral conversion layers for solar cells, lasers and light-emitting devices (LEDs) in the visible and NIR spectral regions.

  • 10.
    Eriksson, Albert
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Development of a Software Tool for Mid-Spatial Frequency Analysis2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The manufacturing of optical components, such as lenses or mirrors, consists of numeroussteps that are essential to the performance of the fnished optical system, such as the specifcation ofthe optical surface. For a longer period, the main focus has been in identifying and restricting thenegative effects of the low and high spatial frequency content of the surface. However, as technologyand optical equipment has become more advanced, the effects of the mid-spatial frequencies havebeen studied more, and continue to be a topic of research. As of now, there is still a need for methodsthat accurately predict and analyse the regime of mid-spatial frequencies, such that they can becontrolled during the specifcation phase, successfully limiting the need of post-processing steps.This work introduces a software tool, specifcally designed to approach this problem, which wasto be developed in Python as a contribution to the existing Optical Scripting Library at OHB. Byspecifying an optical component in terms of a Power Spectral Density function, together with thecontributions from different spatial frequency domains and the application of a ripple patterns, thissoftware tool can generate pseudo-random optical surfaces, which maintains the input specifcations.Furthermore, a Dynamic Link Library fle was developed, sharing the same functionality as thePython implementation, allowing for simulations using Zemax OpticStudio. Using the software tool,it was found that the relative error between input and output measurements were approximately0.78%, in terms of the Power Spectral Density Function. In addition, the result of analysing one of thetwo test cases indicate that the software tool is effective in predicting the infuence of mid-spatialfrequency errors, fulflling a previously measured predicition. The second test case proved that thesoftware tool can be used for mimicing surfaces of real measurements, holding the same specifcations.

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  • 11.
    Eriksson, Ronja
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Direct imaging of Stimulated Raman scattering: 3D spatial control and spatial generation2022Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Stimulated Raman scattering (SRS) is a powerful imaging technique that has become popular during the last decades for its ability to image species specific in a sample with high accuracy. The purpose of this thesis is twofold. Firstly, to demonstrate 3D spatial control of where in the sample SRS is generated. Secondly, the spatial behavior of the SRS generation is investigated by experiments and simulations. SRS is a nonlinear scattering phenomenon that is produced when a sample is illuminated with two laser beams, called Stokes and pump beams, whose frequency difference corresponds to a molecular vibration caused by inelastic scattering of an incoming photon. The Stokes beam will stimulate the scattering of the pump beam photons, which leads to an intensity gain in the Stokes beam and an intensity loss in the pump beam. Imaging of SRS is usually performed by point scanning a sample in a laser scanning microscope by the two laser beams. Thereafter, the image is constructed pixel by pixel by detecting either the gain or the loss. Our aim is to perform direct field of view SRS imaging. Two experimental setups are presented in this thesis, one for the 3D spatial control of SRS and one for the investigation of the spatial generation of SRS.  The working principle of imaging is the same in both setups. A cylindrical sample volume was illuminated with the Stokes beam and the SRS was generated by focusing the pump beam into this volume. The diameter of the illuminated cylinder was around 10 mm. The two beams were combined before the sample using a dichroic mirror and after the sample the pump beam was removed by a second dichroic mirror.  The Stokes light was then image onto a camera providing a field of view of around 9.4 mm by 7.94 mm. A phase spatial light modulator (SLM) was used to control the shape and position of the pump beam in three dimensions (3D) in the illuminated volume. The results show that the SLM allowed for control of the position and shape of the generated SRS signal. In the second experimental setup the pump beam was focused into the sample by a lens and the spatial generation of the SRS was investigated. A second dichroic mirror blocking the pump beam was inserted into the sample at different interaction lengths to study the resulting SRS signal. Further, the pump intensity was varied to study the effect on the physical width of the SRS signal. The experimental results were compared to computer simulations. The simulations were based on diffraction theory for the beam propagation and the interaction between the light beams and the material was modeled with a phase modulation due to the induced Kerr effect caused by high pump intensity. The results shows that most of the SRS generation takes place close to the focus of the pump beam.

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  • 12.
    Eriksson, Ronja
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Evaluation of properties of a digital micromirror device applied for light shaping2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
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  • 13.
    Eriksson, Ronja
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ramser, Kerstin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    3D spatial control and the spatial generation of stimulated Raman scattering in ethanol2022Conference paper (Other academic)
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  • 14.
    Eriksson, Ronja
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ramser, Kerstin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    3D Spatial Control of Stimulated Raman Scattering Using a Phase Spatial Light Modulator2021In: Proceedings OSA Imaging and Applied Optics Congress 2021 (3D, COSI, DH, ISA, pcAOP), Optical Society of America, 2021, article id 3Th2D.4Conference paper (Refereed)
    Abstract [en]

    Species specific 3D imaging requires control of where in the sample stimulated Raman gain is achieved. By using a phase spatial light modulator the signal position can be calculated, controlled and directly imaged in 3D.

     

  • 15.
    Eriksson, Ronja
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ramser, Kerstin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Investigation of the Spatial Generation of Stimulated Raman Scattering Using Computer Simulation and Experimentation2022In: Applied Spectroscopy, ISSN 0003-7028, E-ISSN 1943-3530, Vol. 26, no 11, p. 1307-1316Article in journal (Refereed)
    Abstract [en]

    Stimulated Raman scattering is a phenomenon with potential use in providing real-time molecular information in three-dimensions (3D) of a sample using imaging. For precise imaging, the knowledge about the spatial generation of stimulated Raman scattering is essential. To investigate the spatial behavior in an idealized case, computer simulations and experiments were performed. For the computer simulations, diffraction theory was used for the beam propagation complemented with nonlinear phase modulation describing the interaction between the light and matter. For the experiments, a volume of ethanol was illuminated by an expanded light beam and a plane inside the volume was imaged in transmission. For generating stimulated Raman scattering, a pump beam was focused into this volume and led to a beam dump after passing the volume. The pulse duration of the two beams were 6 ns and the pump beam energy ranged from 1 to 27 mJ. The effect of increasing pump power on the spatial distribution of the Raman gain and the spatial growth of the signal at different interaction lengths between the beam and the sample was investigated. The spatial width of the region where the stimulated Raman scattering signal was generated for experiments and simulation was 0.21 and 0.09 mm, respectively. The experimental and simulation results showed that most of the stimulated Raman scattering is generated close to the pump beam focus and the maximum peak of the Stokes intensity spatially comes shortly after the peak of the pump intensity.

  • 16.
    Etherden, Nicholas
    et al.
    Department of Materials Science, Uppsala University, PO Box 534, S-751 21 Uppsala, Sweden.
    Tesfamichael, T
    Department of Materials Science, Uppsala University, PO Box 534, S-751 21 Uppsala, Sweden.
    Niklasson, G A
    Department of Materials Science, Uppsala University, PO Box 534, S-751 21 Uppsala, Sweden.
    Wäckelgård, E
    Department of Materials Science, Uppsala University, PO Box 534, S-751 21 Uppsala, Sweden.
    A theoretical feasibility study of pigments for thickness-sensitive spectrally selective paints2004In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 37, no 7, p. 1115-1122Article in journal (Refereed)
    Abstract [en]

    We present a model for thickness-sensitive spectrally selective paints and use it to optimize their optical properties with respect to the particle size of the pigment. Pigments were chosen from different classes of materials such as metals, low band gap insulators and semiconductors and carbon. Silicone was chosen as the binder and the paint thickness was varied from 1 to 4 µm. Scattering and absorption cross sections were derived from Mie theory for spherical particles, and the particle radii ranged between 10 and 500 nm. The reflectance was derived from a radiative transfer formulation of a four-flux model, assuming a mono-disperse particle ensemble. The integrated values for near-normal solar absorptance and thermal emittance at 100°C were calculated from the total near-normal spectral reflectance in the wavelength range 0.3–30 µm. It was found that all the pigments investigated have an optimal particle radius of about 100 nm in the case of a 1.0 µm thick paint layer and a particle volume fraction of 0.20. The optimal particle size increases slightly for thicker films. It was also found that direct, low band gap semiconductors give the best spectral selectivity. A solar absorptance of 0.91 and a thermal emittance of 0.13 were computed for PbS particles of volume fraction 0.20 in a 2.0 µm thick paint layer on aluminium.

  • 17.
    Fakhardji, Wissam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Szabo, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza, Egypt. Department of Physics, Faculty of Sciences and Humanity Studies, Huraimla, Shaqra University, Shaqra, Saudi Arabia.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras, Patras, Greece.
    Maroulis, George
    Department of Chemistry, University of Patras, Patras, Greece.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Collision-induced absorption in Ar–Kr gas mixtures: A molecular dynamics study with new potential and dipole data2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, no 14, article id 144303Article in journal (Refereed)
    Abstract [en]

    We have implemented a scheme for classical molecular dynamics simulations of collision-induced absorption. The program has been applied to a gas mixture of argon (Ar) and krypton (Kr). The simulations are compared with accurate quantum dynamical calculations. The comparisons of the absorption coefficients show that classical molecular dynamics is correct within 10% for photon wave numbers up to 220 cm−1 at a temperature of 200 K for this system. At higher temperatures, the agreement is even better. Molecular dynamics accounts for many-body interactions, which, for example, give rise to continuous dimer formation and destruction in the gas. In this way, the method has an advantage compared with bimolecular classical (trajectory) treatments. The calculations are carried out with a new empirical Ar–Kr pair potential. This has been obtained through extensive analysis of experimental thermophysical and transport properties. We also present a new high level ab initio Ar–Kr potential curve for comparison, as well as ab initio interaction-induced dipole curves computed with different methods. In addition, the Ar–Kr polarizability and hyperpolarizability are reported. A comparison of the computed absorption spectra with an experiment taken at 300 K shows satisfactory agreement although a difference in absolute magnitude of 10%–15% persists. This discrepancy we attribute mainly to experimental uncertainty.

  • 18.
    Geng, Wenping
    et al.
    Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
    He, Jinlong
    Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
    Qiao, Xiaojun
    Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
    Niu, Liya
    Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
    Zhao, Caiqin
    Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
    Xue, Gang
    Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
    Bi, Kaixi
    Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
    Mei, Linyu
    School of Mechanical Engineering, North University of China, Taiyuan, 030051, China.
    Wang, Xiangjian
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. School of Materials and Energy, Guangdong University of Technology, Guangzhou, 510006, China.
    Chou, Xiujian
    Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
    Conductive Domain-Wall Temperature Sensors of LiNbO3 Ferroelectric Single-Crystal Thin Films2021In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 42, no 12, p. 1841-1844Article in journal (Refereed)
    Abstract [en]

    Domain wall current (DWC) plays a key role in storage devices, logic devices and sensors due to its high on-off ratio and nano structure size in the era of nanoelectronics technology. In this work, the DWC of single crystal LiNbO3 thin film was studied by piezoresponse force microscope (PFM) and conducting atomic force microscope (c-AFM). We mainly focus on voltage and temperature dependence of DWC which increases with the voltage and temperatures. Based on this research, the packaged DWC temperature sensor is fabricated and applied in wide temperature range. The existence of domain walls makes the current on-off ratio as high as 103 at the voltage of 15 V. Our study shows that DWC has a negative temperature coefficient (NTC) from 140 K to 500 K. The current increases from 3 pA to 57 μA, which is attributed to the conductivity of switched domain. This work proposes a new type temperature sensor with wide temperature range and high compatibility and sensitivity. In addition, it provides support for harsh environment applications of ferroelectric domain engineering devices.

  • 19.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hydrogen dimer features in low temperature collision-induced spectra2017In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 810, no 1, article id 012017Article in journal (Refereed)
    Abstract [en]

    The absorption of radiation in pure hydrogen (H2) gas around the S(0) and S(1) rotational transitions is computed at 20 K and compared with laboratory data. All transitions involving free state are included in the calculations of the absolute absorption. These calculations are done with an isotropic approximation for the H2–H2 pair potential. Agreement with the experiment is observed around the S(0) transition, while the computational approach appears to be slightly worse around the S(1) transition. The positions for bound-to-bound transitions are computed including the full anisotropic pair potential. The anisotropy seems to be crucial to achieve agreement with the measured bound-to-bound transition frequencies. However, those transitions contribute little to the total absorption. The present computed absolute absorptions will provide improved input for radiative transfer models of planetary atmospheres.

  • 20.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza 12211, Egypt.
    Collision-induced absorption in Ar-Xe: a comparative study of empirical and ab initio interaction potentials and electric dipole moments2022In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 292, article id 108362Article in journal (Refereed)
    Abstract [en]

    Empirical Barker-Fisher-Watts and modified Tang-Toennies potential energy curves are obtained through fit to experimental vibrational transition energies for argon–argon, xenon–xenon, and argon–xenon pairs. The potentials are tested against experimental thermophysical and transport properties, and agreement is observed. Also, an interaction-induced electric dipole moment curve for the argon–xenon pair is determined through a fit to experimental spectral moments for collision-induced absorption. The argon–xenon potentials and dipole are tested in a complete quantum dynamical calculation of the collision-induced absorption profiles, which can be compared with a laboratory measurement. This provides further analysis of the accuracy of the empirical argon–xenon data, as calculations of absorption profiles are highly sensitive to the input of molecular data.

  • 21.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Forrey, Robert C.
    Pennsylvania State University, Reading, USA.
    Semiclassical methods for calculating radiative association rate constants for different thermodynamic conditions: Application to formation of CO, CN, and SiN2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, ISSN 0021-9606, Vol. 150, no 22, article id 224301Article in journal (Refereed)
    Abstract [en]

    It is well-known that resonances can serve as a catalyst for molecule formation. Rate constants for resonance-induced molecule formation are phenomenological as they depend upon the mechanism used to populate the resonances. Standard treatments assume tunneling from the continuum is the only available population mechanism, which means long-lived quasibound states are essentially unpopulated. However, if a fast resonance population mechanism exists, the long-lived quasibound states may be populated and give rise to a substantial increase in the molecule formation rate constant. In the present work, we show that the semiclassical formula of Kramers and ter Haar [Bull. Astron. Inst. Neth. 10, 137 (1946)] may be used to compute rate constants for radiative association in the limit of local thermodynamic equilibrium. Comparisons are made with quantum mechanical and standard semiclassical treatments, and results are shown for two limits which provide upper and lower bounds for the six most important radiative association reactions leading to the formation of CO, CN, and SiN. These results may have implications for interstellar chemistry in molecular clouds, where the environmental and thermodynamic conditions often are uncertain.

  • 22.
    Han, Yi
    et al.
    School of Basic Medicine, State Key Laboratory of Bio-Fibers and Eco-Textiles & College of Textiles and Clothes, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, P. R. China.
    Liccardo, Letizia
    Department of Molecular Science and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30172 Venezia Mestre, Italy.
    Moretti, Elisa
    Department of Molecular Science and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30172 Venezia Mestre, Italy.
    Zhao, Haiguang
    School of Basic Medicine, State Key Laboratory of Bio-Fibers and Eco-Textiles & College of Textiles and Clothes, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, P. R. China.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Molecular Science and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30172 Venezia Mestre, Italy.
    Synthesis, optical properties and applications of red/near-infrared carbon dots2022In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Journal of Materials Chemistry C, E-ISSN 2050-7534, Vol. 10, no 33, p. 11827-11847Article, review/survey (Refereed)
    Abstract [en]

    Compared to inorganic quantum dots, fluorescent carbon nanomaterials (C-dots) have gained significant attention because of their unique optoelectrical properties and low toxicity. Although many review articles summarized the last research achievements, only a few of them are focusing on red/near-infrared C-dots. Due to their unique optical and optoelectrical properties in the red/near-infrared region, this interesting subclass of C-dots may be applied as important building blocks for several applications spanning from bioimaging and nano-thermometry, to luminescent solar concentrators (LSCs) and photoelectrochemical systems. Therefore, in this review the synthesis and the fluorescence mechanism together with the most important applications in thermometry, bio-imaging, LSCs and photocatalysis of red/near-infrared C-dots are considered. Furthermore, another aim is to highlight the available approaches to improve the carbonization degree and, additionally, to discuss the structure/composition correlated optical properties. Finally, outlooks, future perspectives and challenges are also discussed for these highly promising nanostructures.

  • 23.
    Hedman, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    A Theoretical Study: The Connection between Stability of Single-Walled Carbon Nanotubes and Observed Products2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the past 20 years’ researchers have tried to utilize the remarkable properties of single-walled carbon nanotubes (SWCNTs) to create new high-tech materials and devices, such as strong light-weight composites, efficient electrical wires and super-fast transistors. But the mass production of these materials and devices are still hampered by the poor uniformity of the produced SWCNTs. These are hollow cylindrical tubes of carbon where the atomic structure of the tube wall consists of just a single atomic layer of carbon atoms arranged in a hexagonal grid. For a SWCNT the orientation of the hexagonal grid making up the tube wall is what determines its properties, this orientation is known as the chirality of a SWCNT. As an example, tubes with certain chiralities will be electrically conductive while others having different chiralities will be semiconducting.

    Today’s large scale methods for producing SWCNTs, commonly known as growth of SWCNTs, gives products with a large spread of different chiralities. A mixture of chiralities will give products with a mixture of different properties. This is one of the major problems holding back the use of SWCNTs in future materials and devices. The ultimate goal is to achieve growth where the resulting product is uniform, meaning that all of the SWCNTs have the same chirality, a process termed chirality-specific growth. To achieve chirality-specific growth of SWCNTs requires us to obtain a better fundamental understanding about how they grow, both from an experimental and a theoretical point of view.

    This work focuses on theoretical studies of SWCNT properties and how they relate to the growth process, thereby giving us vital new information about how SWCNTs grow and taking us ever closer to achieving the ultimate goal of chirality-specific growth. In this thesis, an introduction to the field is given and the current state of the art experiments focusing on chirality-specific growth of SWCNTs are presented. A brief review of the current theoretical works and computer simulations related to growth of SWCNTs is also presented. The results presented in this thesis are obtained using first principle density functional theory. The first study shows a correlation between the stability of SWCNT-fragments and the observed products from experiments. Calculations confirm that in 84% of the investigated cases the chirality of experimental products matches the chirality of the most stable SWCNT-fragments (within 0.2 eV). Further theoretical calculations also reveal a previously unknown link between the stability of SWCNT-fragments and their length. The calculations show that at specific SWCNT-fragment lengths the most stable chirality changes. Thus, introducing the concept of a switching length for SWCNT stability. How these new results link to the existing understanding of SWCNT growth is discussed at the end of the thesis.

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  • 24.
    Hedman, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Linking Stability of Single-Walled Carbon Nanotubes with Growth Products2017Conference paper (Other academic)
    Abstract [en]

    Many of the envisioned products and technologies using single-walled carbon nanotubes (SWCNTs) are only possible with a uniform product. Thus, control over the chirality during catalytical chemical vapor deposition (CCVD) growth of SWCNTs is necessary. Our highlighted works1,2 focuses on stabilities of SWCNTs and how that relates to growth, in order to reach the ultimate goal of chirality-specific growth. In ref.1 density functional theory (DFT) has been used to calculate the stability of SWCNT-fragments of all chiralities in the (n+m) = 8 to 18 series. The fragment stabilities are compare to the chiralities of actual CCVD products from all properly analysed experiments to date. The results show that in 84% of the cases the experimental products represent chiralities among the most stable SWCNT-fragments (within 0.2 eV) from the calculations. The analysed products from growth experiments show that diameters of SWCNTs are governed by the well-known relation to the size of the catalytic particle and that the specific chirality of SWCNT products are strongly dependent on the stability of the tubes within each series, suggesting thermodynamic control at the early stage of growth. Analysis of the relative energy show that for the lower series 8 to 10, zigzag SWCNTs are the most stable and for the higher series 11 to 18 the most stable chirality changes from zigzag to armchair. This switch in stability between armchair and zigzag chiralities is studied further in ref.2, where DFT was used to calculate the stability of armchair and zigzag SWCNTs and graphene nanoribbons (GNRs) of different lengths. The calculations show that the stability of armchair and zigzag tubes has different linear dependence with regard to their length, with switches in the most stable chirality occurring at specific lengths for each SWCNT-series. These dependencies are explained by competing edge and curvature energies. Within each series armchair nanotubes are the most stable at short lengths, while zigzag nanotubes are the most stable at long lengths, this sheds new light into why armchair and near-armchair tubes are the dominant product from CCVD growth, if templating is not used. Paradoxically, the stability of armchair nanotubes at short lengths favors their growth although zigzag nanotubes are more stable at long lengths, resulting in the production of the least stable SWCNTs.

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  • 25.
    Hedman, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    On the Stability of Single-Walled Carbon Nanotubes and how it relates to Growth2017In: CCTN17: 12th International Symposium on Computational Challenges and Tools for Nanotubes, 2017Conference paper (Other academic)
    Abstract [en]

    Many envisioned products and technologies using single-walled carbon nanotubes (SWCNTs) are only possible with a uniform product. Thus, control over the chirality during catalytical chemical vapor deposition (CCVD) growth is necessary. Our highlighted works [1,2] focuses on stabilities of SWCNTs and how they relate to growth. In ref. [1] density functional theory (DFT) is used to calculate the stability of SWCNT-fragments of all chiralities in the 8-18 series. The fragment stabilities are compare with chiralities from actual CCVD products. The results show that 84% of the experimental products represent chiralities among the most stable SWCNT-fragments (within 0.2 eV) from the calculations. The analyzed products from growth experiments show that the chirality of SWCNT products are strongly dependent on the stability of the tubes within each series, suggesting thermodynamic control at the early stage of growth. Analysis of the relative energy show that for lower series 8-10, zigzag SWCNTs are the most stable and for higher series 11-18 the most stable chirality changes from zigzag to armchair. This switch in stability is studied further in ref. [2], where DFT is used to calculate the stability of armchair and zigzag SWCNTs and graphene nanoribbons of different lengths. The calculations show that the stability of armchair and zigzag tubes have different linear dependence with regards to their length, with switches in the most stable chirality occurring at specific lengths for each SWCNT-series. These dependencies are explained by competing edge and curvature energies. Within each series armchair nanotubes are most stable at short lengths, while zigzag nanotubes are most stable at long lengths. This sheds new light into why armchair and near-armchair tubes are dominant products from CCVD growth.

    [1] D. Hedman, H.R Barzegar, A. Rosen, T. Wågberg, J.A Larsson, Sci. Rep., 2015, 5, 16850. [2] D. Hedman, J.A. Larsson, Carbon, 2017, 116, 443.

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  • 26.
    Hedman, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Single-Walled Carbon Nanotubes: A theoretical study of stability, growth and properties2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since their discovery over 25 years ago, scientists have explored the remarkable properties of single-walled carbon nanotubes (SWCNTs) for use in high-tech materials and devices, such as strong light-weight composites, efficient electrical wires, supercapacitors and high-speed transistors. However, the mass production of such materials and devices is still limited by the capability of producing uniform high-quality SWCNTs. The properties of a SWCNT are determined by the orientation of the hexagonal grid of carbon atoms constituting the tube wall, this is known as the chirality of the SWCNT.

    Today's large-scale methods for producing SWCNTs, commonly known as growth, give products with a large spread of different chiralities. A mixture of chiralities give products with a mixture of different properties. This is one of the major obstacles preventing large-scale use of SWCNTs in future materials and devices. The goal is to achieve growth where the resulting product is uniform, meaning that all SWCNTs have the same chirality, a process termed chirality-specific growth. To achieve this requires a deep fundamental understanding of how SWCNTs grow, both from an experimental and a theoretical perspective.

    This work focuses on theoretical studies of SWCNTs and their growth mechanisms. With the goal of achieving a deeper understanding of how chirality arises during growth and how to control it. Thus, taking us ever closer to the ultimate goal of achieving chirality-specific growth. In this thesis, an introduction to the field is given and the current research questions are stated. Followed by chapters on carbon nanomaterials, SWCNTs and computational physics. A review of the state-of-the-art experimental and theoretical works relating to chirality specific growth is also given.

    The results presented in this thesis are obtained using first principle density functional theory calculations. Results show that the stability of short SWCNT-fragments can be linked to the products observed in experiments. In 84% of the investigate cases, the chirality of experimental products matches the chirality of the most stable SWCNT-fragments (within 0.2 eV). Further studies also reveal a previously unknown link between the stability of SWCNT-fragments and their length. Calculations show that at specific lengths the most stable chirality changes. Thus, introducing the concept of a switching length for SWCNT stabilities.

    This newly found property of SWCNTs is used in combination with previously published works to create a state-of-the-art analytical model to investigate growth of SWCNTs any temperature. Results from the model show that the most stable chirality obtained is dependent on the diameter, length of the SWCNT, the growth temperature and the composition of the catalyst. Finally, a detailed study on the ability of catalyst metals to sustain SWCNT growth points to Pt as an interesting candidate to achieve growth of rarely seen chiralities. The new knowledge gained from these results takes us even closer to achieving chirality-specific growth.

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  • 27.
    Jirlén, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kauppi, Emil
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Carbon Nanotube Raman Spectra Calculations using Density Functional Theory2017Student paper otherStudent thesis
    Abstract [en]

    Utilizing density functional theory (DFT) the Vienna Ab initio Simulation Package (VASP) was used to calculate the Raman spectra for five single-walled carbon nanotubes (SWCNTs) with chiralities (4,4), (6,6), (8,0), (12,0) and (7,1). The radial breathing mode (RBM), when compared with experimental frequencies, shows good correlation. When compared to RBM:s calculated with tight binding the frequencies calculated with DFT displayed higher accuracy. The precision of G-band frequencies were inconclusive due to lack of experimental data. The frequencies did not agree well with the results from tight-binding theory. The correctness of the Raman activity estimations using results from DFT calculations was found to be questionable. An unknown mode, which was found to be highly Raman active in the calculated spectra of (4,4), (6,6), and possibly (8,0), and (12,0), is also discussed. It was concluded that further calculations on larger tubes, especially armchair tubes are relevant for future studies. Further verification of the determination of Raman activity is also needed.

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  • 28.
    Karman, Tijs
    et al.
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA; Radboud University, Nijmegen, the Netherlands; Durham University, United Kingdom.
    Gordon, Iouli
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
    van der Avoird, A.
    Radboud University, Nijmegen, the Netherlands.
    Baranov, Yury
    Institute of Experimental Meteorology, Obninsk, Russia.
    Boulet, Christian
    Université Paris-Sud, Orsay, France.
    Drouin, Brian
    Jet Propulsion Laboratory, Caltech, Pasadena, CA, USA.
    Groenenboom, Gerrit
    Radboud University, Nijmegen, the Netherlands.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hartmann, Jean-Michel
    Sorbonne Université, Palaiseau, France.
    Kurucz, Robert
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
    Rothman, Laurence
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
    Sun, Kang
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA; University at Buffalo, Buffalo, NY, USA.
    Sung, Keeyoon
    Jet Propulsion Laboratory, Caltech, Pasadena, CA, USA.
    Thalman, Ryan
    University of Colorado Boulder, Boulder, CO, USA; Snow College, Ephraim, UT, USA.
    Tran, Ha
    Sorbonne Université, Paris, France.
    Wishnow, Edward
    University of California Berkeley, Berkeley, CA, USA.
    Wordsworth, Robin
    Harvard University, Cambridge, MA, USA.
    Vigasin, Andrey
    Russian Academy of Sciences, Moscow, Russia.
    Volkamer, Rainer
    University of Colorado Boulder, Boulder, CO, USA.
    van der Zande, Wim
    Radboud University, Nijmegen, the Netherlands.
    Update of the HITRAN collision-induced absorption section2019In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 328, p. 160-175Article in journal (Refereed)
    Abstract [en]

    Correct parameterization of the Collision-induced Absorption (CIA) phenomena is essential for accurate modeling of planetary atmospheres. The HITRAN spectroscopic database provides these parameters in a dedicated section. Here, we significantly revise and extend the HITRAN CIA data with respect to the original effort described in Richard et al. [JQSRT 113, 1276 (2012)]. The extension concerns new collisional pairs as well as wider spectral and temperature ranges for the existing pairs. The database now contains CIA for N2N2, N2H2, N2-CH4, N2H2O, N2O2, O2O2, O2-CO2, CO2-CO2, H2H2, H2He, H2-CH4, H2H, HHe, CH4-CH4, CH4-CO2, CH4He, and CH4Ar collision pairs. The sources of data as well as their validation and selection are discussed. A wish list to eliminate remaining deficiencies or lack of data from the astrophysics perspective is also presented.

  • 29.
    Kloc, Michal
    et al.
    Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland. Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, Prague, 18000, Czech Republi.
    Šimsa, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Radiation and Chemical Physics, Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
    Hanák, Filip
    Department of Radiation and Chemical Physics, Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
    Kaprálová-Žďánská, Petra Ruth
    Department of Radiation and Chemical Physics, Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
    Stránský, Pavel
    Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, Prague, 18000, Czech Republic.
    Cejnar, Pavel
    Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, Prague, 18000, Czech Republic.
    Quasiclassical approach to quantum quench dynamics in the presence of an excited-state quantum phase transition2021In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 103, no 3, article id 032213Article in journal (Refereed)
    Abstract [en]

    The dynamics of a quantum system following a sudden, highly nonadiabatic change of its control parameter (quantum quench) is studied with quasiclassical techniques. Recent works have shown, using exact quantum mechanical approach, that equilibration after quantum quench exhibits specific features in the presence of excited-state quantum phase transitions. In this paper, we demonstrate that these features can be understood from the classical evolution of the Wigner function in phase space.

  • 30.
    Kumar, Pankaj
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    You, Shujie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, Venezia Mestre, Italy.
    CuSCN as a hole transport layer in an inorganic solution-processed planar Sb2S3 solar cell, enabling carbon-based and semitransparent photovoltaics2022In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 10, no 43, p. 16273-16282Article in journal (Refereed)
    Abstract [en]

    Sb2S3 is an emerging inorganic photovoltaic absorber material with attractive properties such as high absorption coefficient, stability, earth-abundance, non-toxicity, and low-temperature solution processability. Furthermore, with a bandgap of ca. 1.7 eV, it can also be used in semitransparent or tandem solar cell applications. Here, an inorganic wide-bandgap hole transport layer (HTL), copper thiocyanate (CuSCN), is used in an Sb2S3 solar cell employing a simple planar geometry. The compact and highly transparent CuSCN HTL was compatible with the low-cost, blade-coated carbon/Ag electrode and a semitransparent solar cell device. With Au and carbon/Ag electrodes, chemical bath deposited Sb2S3 solar cells achieved power conversion efficiencies (PCEs) of 1.75% and 1.95%, respectively. At the same time, a preliminary semitransparent Sb2S3 device with an ultrathin Au (similar to 15 nm) electrode showed a good average visible transmittance (AVT) of 26.7% at a PCE of 1.65%.

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  • 31.
    Landström, Anton
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Thermal Stability of Carbon Nanotubes and Role of Intercalation2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Research in carbon nanotubes (CNTs) has become a very active field in the past decades, with much interest in their electronic and mechanical properties. However, the thermal properties of CNTs are still not well understood, in particular the process of annealing; i.e. purification of samples by desorption of internal and external impurities. Understanding the response of carbon nanotubes to high temperatures is critical for proper characterization of CNTs and CNT-based materials; especially because purportedly non-destructive characterization techniques such as Raman spectroscopy can induce high temperatures through laser heating. This thesis delineates an experiment aimed at elucidating the annealing and destruction process of carbon nanotubes. The experiment consists of heat treatments of single-walled nanotubes (SWNTs), monitoring nanotube abundance and purity by Raman spectroscopy. The samples are HiPCO-produced SWNTs of very high purity, separated in open and closed (end-capped) tubes. They are wetted with H2O in order to fill the open tubes, but are otherwise kept in their raw (as-produced) form of flakes of bundled tubes. This means that they have a low thermal conductivity as compared to dispersed CNTs, making them sensitive to overheating. The samples are heated in both air and argon environments in order to study the effect of oxidation. It is found that all tubes exhibit some annealing after heat treatment at temperatures as low as 100 °C. Temperatures higher than that are sufficient to degrade the samples in the case of closed tubes, which are found to be more thermally sensitive than open tubes, especially in air environments as oxidation is found to be a major component of the destructive mechanisms of CNTs. With higher temperature heat treatments at 500 °C, some of the open tubes exhibit a further step of annealing. This correlates with tube diameter, thus indicating that this annealing step can be associated with the desorption water from the CNTs' interior. A transition is found after heat treatment at 600 °C, although the new phase is not conclusively established, with evidence pointing to either charge transfer (by way of intercalation of dopant atoms in CNTs) or graphitization. 

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  • 32.
    Laskin, Alexander
    et al.
    AdlOptica GmbH, Rudower Chaussee 29, 12489 Berlin, Germany.
    Volpp, Joerg
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Comparison of the thermal focus shift and aberration between the single-mode and multimode lasers2021In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 33, no 4, article id 042026Article in journal (Refereed)
    Abstract [en]

    Thermal lensing is a well-known but typically undesired effect during the use of laser optics. Nonuniform (gradient) heating due to absorption of high-power laser radiation in optical elements causes thermal lensing, paraxial focus shift, and aberration leading to changes in size and intensity profile of the focused spot in optics. Therefore, an analysis of primary physical effects of geometrical deformation of optical surfaces in the form of aspheric bulges and transformation of the material into a gradient refractive medium was conducted to quantitatively estimate the focus shift and aberrations. Since focus shift effects are different in the case of single-mode and multimode lasers, for both laser modes, the optimal relationships between the physical properties of optical materials for reduction in thermo-optical effects through compensating the material thermal expansion by the change in the refractive index—condition of self-compensation or athermalization were formulated. A comparison of the characteristics, namely, temperature coefficient of the optical pathlength and thermo-optical ratio allowed determination of the optimal materials for the optics for both single-mode and multimode high-power lasers: athermal crystalline quartz and specialty glasses, sapphire with extremely high thermal conductivity ensure minimal temperature gradients. Optics made of these materials exhibit a minimized thermal focus shift and aberration even during the absorption of laser energy in the bulk material and coatings by contamination, scratches, and other surface defects. Weak birefringence of crystalline quartz and sapphire does not prevent their successive use in laser optics.

  • 33.
    Mazza, Francesco
    et al.
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Buurmeijer, Hugo
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Castellanos, Leonardo
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Bohlin, Alexis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Coherent N2+ emission mediated by coherent Raman scattering for gas-phase thermometry2022In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 47, no 23, p. 6105-6108Article in journal (Refereed)
    Abstract [en]

    We report on the generation of coherent emission from femtosecond (fs) laser-induced filaments mediated by ultrabroadband coherent Raman scattering (CRS), and we investigate its application for high-resolution gas-phase thermometry. Broadband 35-fs, 800-nm pump pulses generate the filament through photoionization of the N2 molecules, while narrowband picosecond (ps) pulses at 400 nm seed the fluorescent plasma medium via generation of an ultrabroadband CRS signal, resulting in a narrowband and highly spatiotemporally coherent emission at 428 nm. This emission satisfies the phase-matching for the crossed pump-probe beams geometry, and its polarization follows the CRS signal polarization. We perform spectroscopy on the coherent N2+ signal to investigate the rotational energy distribution of the N2+ ions in the excited B2Σu+ electronic state and demonstrate that the ionization mechanism of the N2 molecules preserves the original Boltzmann distribution to within the experimental conditions tested.

  • 34.
    Mazza, Francesco
    et al.
    Advanced Laser Diagnostics and Flames Laboratory, Aerodynamics, Wind Energy, Flight Performance & Propulsion (AWEP) Department, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, the Netherlands.
    Griffioen, Nathan
    Advanced Laser Diagnostics and Flames Laboratory, Aerodynamics, Wind Energy, Flight Performance & Propulsion (AWEP) Department, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, the Netherlands.
    Castellanos, Leonardo
    Advanced Laser Diagnostics and Flames Laboratory, Aerodynamics, Wind Energy, Flight Performance & Propulsion (AWEP) Department, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, the Netherlands.
    Kliukin, Dmitrii
    Advanced Laser Diagnostics and Flames Laboratory, Aerodynamics, Wind Energy, Flight Performance & Propulsion (AWEP) Department, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, the Netherlands.
    Bohlin, Alexis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Advanced Laser Diagnostics and Flames Laboratory, Aerodynamics, Wind Energy, Flight Performance & Propulsion (AWEP) Department, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, the Netherlands.
    High-temperature rotational-vibrational O2CO2 coherent Raman spectroscopy with ultrabroadband femtosecond laser excitation generated in-situ2022In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 237, article id 111738Article in journal (Refereed)
    Abstract [en]

    We present ultrabroadband two-beam femtosecond/picosecond coherent Raman spectroscopy on the ro-vibrational spectra of CO2 and O2, applied for multispecies thermometry and relative concentration measurements in a standard laminar premixed hydrocarbon flame. The experimental system employs fs-laser-induced filamentation to generate the compressed supercontinuum in-situ, resulting in a ∼24 fs full-width-at-half-maximum pump/Stokes pulse with sufficient bandwidth to excite all the ro-vibrational Raman transitions up to 1600 cm-1. We report the simultaneous recording of the ro-vibrational CO2 Q-branch and the ro-vibrational O2 O-, Q- and S-branch coherent Stokes Raman spectra (CSRS) on the basis of a single-laser-shot. The use of filamentation as the supercontinuum generation mechanism has the advantage of greatly simplifying the experimental setup, as it avoids the use of hollow-core fibres and chirped mirrors to deliver a near-transform-limited ultrabroadband pulse at the measurement location. Time-domain models for the ro-vibrational Q-branch spectrum of CO2 and the ro-vibrational O-, Q- and S-branch spectra of O2 were developed. The modelling of the CO2 Q-branch spectrum accounts for up to 180 vibrational bands and for their interaction in Fermi polyads, and is based on recently available, comprehensive calculations of the vibrational transition dipole moments of the CO2 molecule: the availability of spectroscopic data for these many vibrational bands is crucial to model the high-temperature spectra acquired in the flue gases of hydrocarbon flames, where the temperature can exceed 2000 K. The numerical code was employed to evaluate the CSRS spectra acquired in the products of a laminar premixed methane/air flame provided on a Bunsen burner, for varying equivalence ratio in the range 0.6–1.05. The performance of the CO2 spectral model is assessed by extracting temperatures from 40-laser-shots averaged spectra, resulting in thermometry accuracy and precision of ∼5% and ∼1%, respectively, at temperatures as high as 2220 K.

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  • 35.
    Mazza, Francesco
    et al.
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Stutvoet, Aert
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Castellanos, Leonardo
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Kliukin, Dmitrii
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands; LaserLaB, Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
    Bohlin, Alexis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Coherent Raman spectroscopy on hydrogen with in-situ generation, in-situ use, and in-situ referencing of the ultrabroadband excitation2022In: Optics Express, E-ISSN 1094-4087, Vol. 30, no 20, p. 35232-35245Article in journal (Refereed)
    Abstract [en]

    Time-resolved spectroscopy can provide valuable insights in hydrogen chemistry, with applications ranging from fundamental physics to the use of hydrogen as a commercial fuel. This work represents the first-ever demonstration of in-situ femtosecond laser-induced filamentation to generate a compressed supercontinuum behind a thick optical window, and its in-situ use to perform femtosecond/picosecond coherent Raman spectroscopy (CRS) on molecular hydrogen (H2). The ultrabroadband coherent excitation of Raman active molecules in measurement scenarios within an enclosed space has been hindered thus far by the window material imparting temporal stretch to the pulse. We overcome this challenge and present the simultaneous single-shot detection of the rotational H2 and the non-resonant CRS spectra in a laminar H2/air diffusion flame. Implementing an in-situ referencing protocol, the non-resonant spectrum measures the spectral phase of the supercontinuum pulse and maps the efficiency of the ultrabroadband coherent excitation achieved behind the window. This approach provides a straightforward path for the implementation of ultrabroadband H2 CRS in enclosed environment such as next-generation hydrogen combustors and reforming reactors.

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  • 36.
    Mazza, Francesco
    et al.
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Thornquist, Ona
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Castellanos, Leonardo
    Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    Butterworth, Thomas
    Faculty of Science and Engineering, Maastricht University, Paul Henri Spaaklaan 1, 6229 GS Maastricht, The Netherlands.
    Richard, Cyril
    Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS–Université Bourgogne Franche-Comté, 9 Avenue Alain Savary, BP 47 870, F-21078 Dijon Cedex, France.
    Boudon, Vincent
    Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS–Université Bourgogne Franche-Comté, 9 Avenue Alain Savary, BP 47 870, F-21078 Dijon Cedex, France.
    Bohlin, Alexis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands.
    The ro-vibrational ν2 mode spectrum of methane investigated by ultrabroadband coherent Raman spectroscopy2023In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 158, no 9, article id 094201Article in journal (Refereed)
    Abstract [en]

    We present the first experimental application of coherent Raman spectroscopy (CRS) on the ro-vibrational ν2 mode spectrum of methane (CH4). Ultrabroadband femtosecond/picosecond (fs/ps) CRS is performed in the molecular fingerprint region from 1100 to 2000 cm−1, employing fs laser-induced filamentation as the supercontinuum generation mechanism to provide the ultrabroadband excitation pulses. We introduce a time-domain model of the CH4 ν2 CRS spectrum, including all five ro-vibrational branches allowed by the selection rules Δv = 1, ΔJ = 0, ±1, ±2; the model includes collisional linewidths, computed according to a modified exponential gap scaling law and validated experimentally. The use of ultrabroadband CRS for in situ monitoring of the CH4 chemistry is demonstrated in a laboratory CH4/air diffusion flame: CRS measurements in the fingerprint region, performed across the laminar flame front, allow the simultaneous detection of molecular oxygen (O2), carbon dioxide (CO2), and molecular hydrogen (H2), along with CH4. Fundamental physicochemical processes, such as H2 production via CH4 pyrolysis, are observed through the Raman spectra of these chemical species. In addition, we demonstrate ro-vibrational CH4 v2 CRS thermometry, and we validate it against CO2 CRS measurements. The present technique offers an interesting diagnostics approach to in situ measurement of CH4-rich environments, e.g., in plasma reactors for CH4 pyrolysis and H2 production.

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  • 37.
    Naseem, Shahnila
    et al.
    Department of Physics, University of Sargodha, 40100 Sargodha, Pakistan.
    Alay-e-Abbas, Syed Muhammad
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Computational Materials Modeling Laboratory, Department of Physics, Government College University Faisalabad, 38040 Faisalabad, Pakistan.
    Nazir, S.
    Department of Physics, University of Sargodha, 40100 Sargodha, Pakistan.
    Thermodynamics and a definite large half-metallic spin gap along with a magnetic anisotropy in La-doped Ba2NiIrO62023In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 160, article id 107425Article in journal (Refereed)
  • 38.
    Pignatelli, F.
    et al.
    Division of Fluid Mechanics, Department of Energy Sciences, Lund University, Lund, Sweden.
    Derafshzan, S.
    Division of Combustion Physics, Department Physics, Lund University, Lund, Sweden.
    Sanned, D.
    Division of Combustion Physics, Department Physics, Lund University, Lund, Sweden.
    Papafilippou, Nikolaos
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Szasz, R. Z.
    Division of Fluid Mechanics, Department of Energy Sciences, Lund University, Lund, Sweden.
    Chishty, M. A.
    Research Institutes of Sweden (RISE), Piteå 941 38, Sweden.
    Petersson, P.
    Dantec Dynamics A/S, Skovlunde, Denmark.
    Bai, X. S.
    Division of Fluid Mechanics, Department of Energy Sciences, Lund University, Lund, Sweden.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ehn, A.
    Division of Combustion Physics, Department Physics, Lund University, Lund, Sweden.
    Richter, M.
    Division of Combustion Physics, Department Physics, Lund University, Lund, Sweden.
    Lörstad, D.
    Siemens Energy AB, Finspång, Sweden.
    Subash, A. A.
    Division of Combustion Physics, Department Physics, Lund University, Lund, Sweden.
    Effect of CO2 dilution on structures of premixed syngas/air flames in a gas turbine model combustor2023In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 255, article id 112912Article in journal (Refereed)
    Abstract [en]

    The impact of CO2 dilution on combustion of syngas (a mixture of H2, CO, and CH4) was investigated in a lab-scale gas turbine model combustor at atmospheric pressure conditions. Two mild dilution levels of CO2, corresponding to 15% and 34% of CO2 mole fraction in the syngas/CO2 mixtures, were experimentally investigated to evaluate the effects of CO2 dilution on the flame structures and the emissions of CO and NOx. All experiments were performed at a constant Reynolds number (Re = 10000). High-speed flame luminescence, simultaneous planar laser-induced fluorescence (PLIF) measurements of the OH radicals and particle image velocimetry (PIV) were employed for qualitative and quantitative assessment of the resulting flame and flow structures. The main findings are: (a) the operability range of the syngas flames is significantly affected by the CO2 dilution, with both the lean blowoff (LBO) limit and the flashback limit shifting towards fuel-richer conditions as the CO2 dilution increases; (b) syngas flames exhibit flame-pocket structures with chemical reactions taking place in isolated pockets surrounded by non-reacting fuel/air mixture; (c) the inner recirculation zone tends to move closer to the burner axis at high CO2 dilution, and (d) the NOx emission becomes significantly lower with increasing CO2 dilution while the CO emission exhibits the opposite trend. The flame-pocket structure is more significant with increased CO2 dilution level. The low NOx emissions and high CO emissions are the results of the flame-pocket structures.

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  • 39.
    Sarman, Sten
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden.
    Laaksonen, Aatto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden; Centre of Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry, Aleea Grigore Ghica-Voda, 41A, 700487 Iasi, Romania; State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, 210009, P. R. China; Department of Chemical and Geological Sciences, University of Cagliari, Campus Monserrato, SS 554 Bivio per Sestu, 09042, Monserrato, Italy.
    Diffusion-driven rotation in cholesteric liquid crystals studied using molecular dynamics simulation of a mixture of the Gay-Berne fluid and the Lennard-Jones fluid2023In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 25, no 28, p. 18833-18843Article in journal (Refereed)
    Abstract [en]

    Diffusion-driven rotation in cholesteric liquid crystals has been studied using molecular dynamics simulation. Then a chemical potential gradient parallel to the cholesteric axis induces a torque that rotates the director at a constant rate around this axis, besides driving a mass current. An equimolar mixture of Gay-Berne ellipsoids and Lennard-Jones spheres was used as the molecular model. In order to keep the system homogeneous, the color conductivity algorithm was used to apply a color field instead of a chemical potential gradient to drive a mass current. Then the particles are given a color charge that interacts with a color field in the same way as with an electric field, but these charges do not interact with each other. This algorithm is often used to calculate the mutual diffusion coefficient. In the above liquid crystal model, it was found that the color field induces a torque that rotates the director at a constant rate around the cholesteric axis in addition to driving a mass current. The phenomenon was quantified by calculating the cross-coupling coefficient between the color field and the director angular velocity. The results were cross-checked by using a director rotation algorithm to exert a torque to rotate the director at a constant rate. Besides rotation of the director, this resulted in a mass current parallel to the cholesteric axis. The cross-coupling coefficient between the torque and the mass current was equal to the cross-coupling coefficient between the color field and the director rotation rate within a statistical uncertainty of 10 percent, thus fulfilling the Onsager reciprocity relations. As a further cross-check, these cross-coupling coupling coefficients, the color conductivity, and the twist viscosity were calculated by evaluating the corresponding Green-Kubo relations. Finally, it was noted that the orientation of the cholesteric axis parallel to the color field is the one that minimizes the irreversible energy dissipation rate. This is in accordance with a theorem stating that this quantity is minimal in the linear regime of a nonequilibrium steady state.

  • 40.
    Sollén, Sofia
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Eppanapelli, Lavan Kumar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Pettersson, Jennifer
    Division of Rotating Machines, Vattenfall AB, Asset Development - R&D, Solna, Sweden.
    Ukonsaari, Jan
    Division of Rotating Machines, Vattenfall AB, Asset Development - R&D, Luleå, Sweden.
    Attermo, Pär
    Division of Businesses Area Wind, Vattenfall AB, Solna, Sweden.
    Experimental Investigation of an Infrared Deicing System for Wind Power Application in a Cold Climate2022In: Journal of cold regions engineering, ISSN 0887-381X, E-ISSN 1943-5495, Vol. 36, no 4, article id 04022008Article in journal (Refereed)
    Abstract [en]

    Icing of wind turbine blades poses a great challenge for wind farms in cold climates, this challenge is addressed by implementing various deicing practices that require significant cost to operate. Thus, alternative and potential solutions are needed to improve wind power production in cold climate. The present study is investigates the effectiveness of a new deicing system consisting of infrared heaters. Two types of heaters were selected based on wavelength, input power, and investment cost. The heaters were tested on blades covered with soft rime ice. A thermal camera was used to image the deicing procedure together with a load cell to measure the weight of the ice melted. It was found that a combination of two different types of heaters provides effective deicing at a distance of 1.5 m compared with multiple units of the same type of heaters. It was observed that the infrared deicing system has a larger area of heat distribution, which is one of the major advantages compared with traditional systems. © 2022 American Society of Civil Engineers.

  • 41.
    Szabo, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Formation of the NH molecule and its isotopologues through radiative association2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 483, no 3, p. 3574-3578Article in journal (Refereed)
    Abstract [en]

    The rate coefficients and the cross-sections for the formation of imidogen (NH) molecule (and its isotopologues: 15NH and ND) through radiative association are determined by employing quantum mechanical perturbation theory, classical Larmor formula, and Breit–Wigner theory. We suggest the radiative association process as possible route for NH production in diffuse interstellar clouds.

  • 42.
    Szabo, Peter
    et al.
    Department of Physics and Materials Science, University of Luxembourg, Luxembourg, Luxembourg.
    Góger, Szabolcs
    Research Ctr. for Natural Sciences, Institute of Materials and Environmental Chemistry, Hungarian Academy of Sciences, Budapest, Hungary.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Formation of the BeH+ and BeD+ Molecules in Be+ + H/D Collisions Through Radiative Association2021In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 8, article id 704953Article in journal (Refereed)
    Abstract [en]

    Cross sections and rate coefficients for the formation of BeH+ and BeD+ molecules in Be+ + H/D collisions through radiative association are calculated using quantum mechanical perturbation theory and Breit-Wigner theory. The local thermodynamic equilibrium limit of the molecule formation is also studied, since the process is also relevant in environments with high-density and/or strong radiation fields. The obtained rate coefficients may facilitate the kinetic modelling of BeH+/BeD+ production in astrochemical environments as well as the corrosion chemistry of thermonuclear fusion reactors.

  • 43.
    Taranova, Anastasiia
    et al.
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172, Venice, Italy View author publications.
    Akbar, Kamran
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172, Venice, Italy.
    Yusupov, Khabib
    Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83, Linköping, Sweden.
    You, Shujie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Polewczyk, Vincent
    Istituto Officina dei Materiali (IOM) - CNR, Laboratorio TASC, Area Science Park, S.S. 14 Km 163.5, Trieste, I-34149, Italy.
    Mauri, Silvia
    Istituto Officina dei Materiali (IOM) - CNR, Laboratorio TASC, Area Science Park, S.S. 14 Km 163.5, Trieste, I-34149, Italy; Dipartimento di Fisica, University of Trieste, via A. Valerio 2, 34127, Trieste, Italy.
    Balliana, Eleonora
    Department of Environmental Sciences, Informatics and Statistics, Ca’ Foscari University of Venice, Scientific Campus Via Torino 155/b, 30173, Venice, Italy.
    Rosen, Johanna
    Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83, Linköping, Sweden.
    Moras, Paolo
    Istituto di Struttura della Materia (ISM) - CNR, S.S. 14 Km 163.5, Trieste, I-34149, Italy.
    Gradone, Alessandro
    Istituto per la Microelettronica ed i Microsistemi (IMM) – CNR Sede di Bologna, via Gobetti 101, 40129, Bologna, Italy.
    Morandi, Vittorio
    Istituto per la Microelettronica ed i Microsistemi (IMM) – CNR Sede di Bologna, via Gobetti 101, 40129, Bologna, Italy.
    Moretti, Elisa
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172, Venice, Italy.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172, Venice, Italy.
    Unraveling the optoelectronic properties of CoSbx intrinsic selective solar absorber towards high-temperature surfaces2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 7280Article in journal (Refereed)
    Abstract [en]

    The combination of the ability to absorb most of the solar radiation and simultaneously suppress infrared re-radiation allows selective solar absorbers (SSAs) to maximize solar energy to heat conversion, which is critical to several advanced applications. The intrinsic spectral selective materials are rare in nature and only a few demonstrated complete solar absorption. Typically, intrinsic materials exhibit high performances when integrated into complex multilayered solar absorber systems due to their limited spectral selectivity and solar absorption. In this study, we propose CoSbx (2 < x < 3) as a new exceptionally efficient SSA. Here we demonstrate that the low bandgap nature of CoSbx endows broadband solar absorption (0.96) over the solar spectral range and simultaneous low emissivity (0.18) in the mid-infrared region, resulting in a remarkable intrinsic spectral solar selectivity of 5.3. Under 1 sun illumination, the heat concentrates on the surface of the CoSbx thin film, and an impressive temperature of 101.7 °C is reached, demonstrating the highest value among reported intrinsic SSAs. Furthermore, the CoSbx was tested for solar water evaporation achieving an evaporation rate of 1.4 kg m−2 h−1. This study could expand the use of narrow bandgap semiconductors as efficient intrinsic SSAs with high surface temperatures in solar applications.

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  • 44.
    Volpp, Joerg
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    High-temperature laser absorption of steel2023In: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, Institute of Electrical and Electronics Engineers Inc. , 2023Conference paper (Refereed)
  • 45.
    Volpp, Joerg
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Laser beam absorption measurement at molten metal surfaces2023In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 209, article id 112524Article in journal (Refereed)
    Abstract [en]

    Laser light absorption is one of the elementary effects of laser material processing. Absorption values are relevant to calculate the process efficiency and predict the impact on the material for the increasingly used laser processes. However, absorption measurement can be a complex task. At high temperatures of metals, only limited experimental data is available due to the dynamic surfaces and the often unknown emissivity needed for the temperature measurement. Models were created to predict the absorption at different temperatures, which are successful with assumptions in some regimes, but often fail in others. For improving the theoretical models, an experimental measurement of high-temperature metal surfaces is desired. Therefore, a radiometric measurement method is proposed in this work using a heating laser to create a metal melt pool, while measuring temperature and reflection of its surface by a second measuring laser beam. General tendencies known from literature could be confirmed by the measurements, while absorption values tend to scatter at increasing temperature. However, trends could be observed. Between melting and boiling temperature, a slight absorption increase was seen in the range between 35% and 38%. Those values indicate that both interband and intraband absorption must be considered to explain the absorption in this regime. At increased temperatures, the intraband absorption becomes the dominating absorption mechanism, reaching absorption values above 45% at very high temperatures.

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  • 46.
    Volpp, Joerg
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Laser light absorption of high-temperature metal surfaces2023In: Heliyon, E-ISSN 2405-8440, Vol. 9, no 10, article id e21021Article in journal (Refereed)
    Abstract [en]

    Laser beam absorption is the basic effect to enable many high-temperature applications and processes. However, high temperature absorption data of metals is often not available or based on theoretical assumptions. In this work, using a newly developed experimental arrangement to measure laser light absorption on liquid metal surfaces even above boiling temperature enabled the derivation of absorption values in those regimes. Results indicate that interband absorption must be considered even at such high temperatures against common theoretical predictions. It is shown that the simulated nearly constant absorption depth and absorption values between melting and boiling temperatures indicate that the increased atom distance due to thermal expansion, denoting a reduced absorption volume, is counterbalanced by the increased statistical availability of conduction electrons due to Fermi band broadening.

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  • 47.
    Widerström, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Entangled photon triplets produced by a third order SPDC process2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis describes the work performed at the Quantum Optics lab at UNAM,Mexico City. Third order spontaneous parametric down conversion (TOSPDC) isa quantum optical process where an incoming photon is annihilated and generatesthree quantum entangled photons, so called photon triplets, under energy and mo-mentum conservation. This TOSPDC process was experimentally realized using afused silica optical fiber as nonlinear source. The spectra of the emitted signal weremeasured and coincidence counts measurements were performed in order to verifythe generation of these triplets. An average of 0.8 triplets per second were detected,which is the first sign of a realized TOSPDC process to our knowledge. At thispoint, the signal was too low for any spectra to be recorded. There is a lot of roomfor improvements, especially regarding the equipment used due to the heavy signalloss throughout the experimental setup, and more experiments will be performed toproperly verify the production and entanglement of the triplet photons.

  • 48.
    Zulfiqar, Waqas
    et al.
    Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Faisalabad, Pakistan; Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
    Alay-e-Abbas, Syed Muhammad
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Faisalabad, Pakistan.
    Improved Thermodynamic Stability and Visible Light Absorption in Zr+X Codoped (X = S, Se and Te) BaTiO3 Photocatalysts: A First-Principles Study2022In: Materials Today Communications, ISSN 2352-4928, Vol. 32, article id 103867Article in journal (Refereed)
    Abstract [en]

    Band gap tuning of titanium based perovskite oxides through chalcogen doping is an attractive avenue for realizing visible light driven photocatalysis for hydrogen production. Unfortunately, accommodating a chalcogen atom at an O-site of BaTiO3 is thermodynamically challenging owing to large differences in the atomic radii and electronegativities of oxygen and chalcogen atoms. In the present study we employ first-principles density functional theory calculations to examine the influence of Zr codoping on the structural, thermodynamic, opto-electronic properties and photocatalytic performance of X-doped (X = S, Se and Te) BaTiO3 systems. The atomic structure and energetic properties are computed using SCAN meta-GGA functional of density functional theory, while the electronic and optical properties are computed using the TB-mBJ meta-GGA potential functional. Within the valid limits of the atomic chemical potentials, we find that chalcogen doping in BaTiO3 lattice would be experimentally difficult despite a clear reduction in the electronic band gap of this system useful for application in visible light driven photocatalysis. In order to improve the synthesis feasibility of X-doped BaTiO3 under oxygen-rich as well as oxygen-poor chemical environments, we propose Zr as a codopant at a Ti-site in X-doped BaTiO3 which improves the thermodynamic stability and also retains the reduction in the electronic band gap of BaTiO3 caused by the presence of chalcogen atom. Our results suggest that Zr+X (X = S, Se and Te) codoped BaTiO3 offers great opportunities as a practical photocatalysts for hydrogen production through overall splitting of the water molecule.

  • 49.
    Zámečníková, Martina
    et al.
    Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
    Soldán, Pavel
    Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
    Formation of CO+ by radiative association II2020In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 492, no 3, p. 3794-3802Article in journal (Refereed)
    Abstract [en]

    Radiative association of an oxygen atom with a carbon cation is investigated using quantal and semiclassical methods. The total rate coefficient for spontaneous radiative association of O(2s22p4, 3P) with C+(2s22p, 2P) on the doublet manifold is determined from the corresponding cross-sections. The cross-sections for the 12 Σ - → A2 II, 22 Σ - → A2II, and C2 Δ → A2II continuum-bound processes are calculated either semiclassically, in combination with the Breit-Wigner approach, or fully quantum mechanically. In the temperature range 10-10 000 K, our recommended total rate coefficient, obtained from these calculations and the data of Zámecniková et al. (2019), slowly increases from 7.5 × 10-18 cm3s-1 to 2.1 × 10-17 cm3s-1. Corresponding aspects of the CO+ and CO formations in SN 1987A are discussed

  • 50.
    Öhman, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Polarization-resolved dual-view holographic system for 3D inspection of scattering particles2019In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 58, no 34, p. G31-G40Article in journal (Refereed)
    Abstract [en]

    A novel dual-view polarization-resolved pulsed holographic system for particle measurements is presented. Both dual-view configuration and polarization-resolved registration are well suited for particle holography. Dual-view registration improves the accuracy in the detection of 3D position and velocities, and polarization-resolved registration provides polarization information about individual particles. The necessary calibrations are presented, and aberrations are compensated for by mapping the positions in the two views to positions in a global coordinate system. The system is demonstrated on a sample consisting of 7 μm spherical polystyrene particles dissolved in water in a cuvette. The system is tested with different polarizations of the illumination. It is found that the dual view improves the accuracy significantly in particle tracking. It is also found that by having polarization-resolved holograms, it is possible to separate naturally occurring sub-micrometer particles from the larger, 7 μm seeding particles.

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