The Experts below are selected from a list of 10428 Experts worldwide ranked by ideXlab platform
Xin Wei - One of the best experts on this subject based on the ideXlab platform.
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Influence of Beam Polarizations on Evaporative Laser Cutting Nonmetallic Materials within High Absorptance
Materials Science Forum, 2009Co-Authors: Xiao-zhu Xie, Xin WeiAbstract:The three dimensional (3D) coupling model is set up for analyzing the energy reflection and absorption on the kerf using ray tracing method after the laser beam cutting nonmetallic materials with high absorptance through multiple reflections. The laser beam characterized by focused gauss beam and fresnel absorption on the kerf are taken into account. The influences of the polarization on the Absorbed Intensity both in the front and the two walls are also discussed. Results indicate the differences of absorptive Intensity among the three polarized lights are relatively small compared to metal. Thus, the polarization has little effects on the kerf of nonmetallic materials with high absorptance. The experimental results also agree well with the theoretical analysis.
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Distribution of the Intensity Absorbed by evaporative front in laser cutting nonmetallic material
Optics and Lasers in Engineering, 2008Co-Authors: Xiao-zhu Xie, Xin WeiAbstract:The distribution of the Intensity Absorbed by the evaporative cutting front is investigated using ray-tracing method after the laser beam undergoes multiple reflections in an actual kerf photographed experimentally. The laser beam is characterized by focused Gauss beam. Fresnel absorption on the kerf is taken into account, while inverse bremsstrahlung absorption is negligible. The influences of the times of multiple reflections and laser beam's position on the Absorbed Intensity are also discussed. Results indicate front Intensity absorption is mainly determined by the first three incident beams. The laser axis moves toward the front, which is affected by the cutting speed.
Xiao-zhu Xie - One of the best experts on this subject based on the ideXlab platform.
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Influence of Beam Polarizations on Evaporative Laser Cutting Nonmetallic Materials within High Absorptance
Materials Science Forum, 2009Co-Authors: Xiao-zhu Xie, Xin WeiAbstract:The three dimensional (3D) coupling model is set up for analyzing the energy reflection and absorption on the kerf using ray tracing method after the laser beam cutting nonmetallic materials with high absorptance through multiple reflections. The laser beam characterized by focused gauss beam and fresnel absorption on the kerf are taken into account. The influences of the polarization on the Absorbed Intensity both in the front and the two walls are also discussed. Results indicate the differences of absorptive Intensity among the three polarized lights are relatively small compared to metal. Thus, the polarization has little effects on the kerf of nonmetallic materials with high absorptance. The experimental results also agree well with the theoretical analysis.
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Distribution of the Intensity Absorbed by evaporative front in laser cutting nonmetallic material
Optics and Lasers in Engineering, 2008Co-Authors: Xiao-zhu Xie, Xin WeiAbstract:The distribution of the Intensity Absorbed by the evaporative cutting front is investigated using ray-tracing method after the laser beam undergoes multiple reflections in an actual kerf photographed experimentally. The laser beam is characterized by focused Gauss beam. Fresnel absorption on the kerf is taken into account, while inverse bremsstrahlung absorption is negligible. The influences of the times of multiple reflections and laser beam's position on the Absorbed Intensity are also discussed. Results indicate front Intensity absorption is mainly determined by the first three incident beams. The laser axis moves toward the front, which is affected by the cutting speed.
Thomas Graf - One of the best experts on this subject based on the ideXlab platform.
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Influence of the Real Geometry of the Laser Cut Front on the Absorbed Intensity and the Gas Flow
Lasers in Manufacturing and Materials Processing, 2019Co-Authors: Oliver Bocksrocker, Peter Berger, Florian Fetzer, Volker Rominger, Thomas GrafAbstract:The numerical investigations on experimentally determined cut front geometries presented in this paper show that the Absorbed Intensity reacts more sensitively to small local changes of the angle of the cut front than the gas velocity and the pressure. It is also found that the Absorbed intensities near the top and the bottom of the cut front increase significantly when the initially regular process at high cutting speeds turns into the regime with interrupted striation patterns on the surface of the cutting edge.
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Comparison between ray-tracing and physical optics for the computation of light absorption in capillaries – the influence of diffraction and interference
Optics express, 2012Co-Authors: Yuan Qin, Andreas Michalowski, Rudolf Weber, Sen Yang, Thomas GrafAbstract:Ray-tracing is the commonly used technique to calculate the absorption of light in laser deep-penetration welding or drilling. Since new lasers with high brilliance enable small capillaries with high aspect ratios, diffraction might become important. To examine the applicability of the ray-tracing method, we studied the total absorptance and the Absorbed Intensity of polarized beams in several capillary geometries. The ray-tracing results are compared with more sophisticated simulations based on physical optics. The comparison shows that the simple ray-tracing is applicable to calculate the total absorptance in triangular grooves and in conical capillaries but not in rectangular grooves. To calculate the distribution of the Absorbed Intensity ray-tracing fails due to the neglected interference, diffraction, and the effects of beam propagation in the capillaries with sub-wavelength diameter. If diffraction is avoided e.g. with beams smaller than the entrance pupil of the capillary or with very shallow capillaries, the distribution of the Absorbed Intensity calculated by ray-tracing corresponds to the local average of the interference pattern found by physical optics.
Marc A. Baldo - One of the best experts on this subject based on the ideXlab platform.
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Solid-state infrared-to-visible upconversion sensitized by colloidal nanocrystals
Nature Photonics, 2016Co-Authors: Daniel N. Congreve, Mark W. B. Wilson, Joel Jean, Nadav Geva, Matthew Welborn, Troy Van Voorhis, Vladimir Bulović, Moungi G. Bawendi, Marc A. BaldoAbstract:Optical upconversion via sensitized triplet–triplet exciton annihilation converts incoherent low-energy photons to shorter wavelengths under modest excitation intensities^ 1 , 2 , 3 . Here, we report a solid-state thin film for infrared-to-visible upconversion that employs lead sulphide colloidal nanocrystals as a sensitizer. Upconversion is achieved from pump wavelengths beyond λ = 1 μm to emission at λ = 612 nm. When excited at λ = 808 nm, two excitons in the sensitizer are converted to one higher-energy state in the emitter at a yield of 1.2 ± 0.2%. Peak efficiency is attained at an Absorbed Intensity equivalent to less than one sun. We demonstrate that colloidal nanocrystals are an attractive alternative to existing molecular sensitizers, given their small exchange splitting, wide wavelength tunability, broadband infrared absorption, and our transient observations of efficient energy transfer. This solid-state architecture for upconversion may prove useful for enhancing the capabilities of solar cells and photodetectors. Lead sulphide colloidal nanocrystals offer a solid-state answer for infrared-to-visible upconversion.
R. Sauerbrey - One of the best experts on this subject based on the ideXlab platform.
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Angle-dependent X-ray emission and resonance absorption in a laser-produced plasma generated by a high Intensity ultrashort pulse.
Physical review letters, 1993Co-Authors: U. Teubner, J. Bergmann, B. Van Wonterghem, F. P. Schäfer, R. SauerbreyAbstract:Plasmas were generated by 400 fs KrF laser pulses at intensities of \ensuremath{\sim}${10}^{17}$ W ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ on aluminum targets. Reflectivity and x-ray emission were measured as a function of laser polarization, angle of incidence, and Intensity. For the same Absorbed Intensity, p-polarized laser light is up to a factor of 5 more efficient in generating x rays (g0.5 keV) than s-polarized light. These results show the importance of an additional absorption process, besides collisional absorption, for short scale length plasmas that is effective for p-polarized light only and has the characteristics of resonance absorption.
