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Multi-physical analysis of thermo-optical effects for different Selective Laser Melting (SLM) scanning strategies
摘要： In this paper, transient thermo-optical effects in protective windows for selective laser melting are analyzed by means of a multi-physical analysis. The temperature distribution of the window is simulated for different scanning strategies and orders of exposure. Therefore, cubic test specimens are virtually built and the resulting axial and lateral focus shift is analyzed. Furthermore, the impact of the distance between the laser scanner and the protective window is analyzed. The simulations predict that spreading the thermal load on the window both spatially and temporally reduces the focus shift. Consequently, the focus shift is reduced if the window is placed further away from the laser scanner.
关键词： thermal lensing,Selective laser melting,protective window,finite element analysis,laser-powder bed fusion,additive manufacturing
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Population Lensing in Alexandrite Lasers
摘要： Alexandrite (Cr3+:BeAl2O4) is a vibronic laser at 701-858 nm. Its excellent thermo-mechanical properties and high energy storage make it an ideal high power and high energy Q-switched source with recent development in mJ-level red-diode-pumped Alexandrite oscillators and amplifiers [1-3]. Further power scaling of these systems is limited by thermal lensing which has yet to be addressed in great detail. In this work we present experimental and finite element analysis (FEA) results on the investigation of thermal lensing in a red-diode-pumped Alexandrite laser. Differences in the thermal lensing power for non-lasing and lasing conditions are attributed to a ‘population lens’ effect. In a separate study stable self-Q-switching (SQS) is observed in an Alexandrite laser cavity containing only the gain medium where the SQS loss mechanism is attributed to the population lens.
关键词： self-Q-switching,diode-pumped,population lens,thermal lensing,Alexandrite
更新于2025-09-12 10:27:22
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Multi-channel averaging detection for fast imaging of weakly absorbing defects in surface thermal lensing
摘要： Surface thermal lensing (STL) is a high sensitive pump-probe technique for photothermal characterization of weakly absorbing defects in optical materials. Commonly, the frequency modulation is applied in the pump beam, and the STL signal that appears as small modulation on top of an intense background is then detected on the probe beam by lock-in amplification. However, the lock-in detection by filtering the signal in the frequency domain results in low efficiency in the STL, preventing investigations of the large area surfaces. Here it is shown that the multi-channel averaging, which corresponds to temporal integration, is better suited for detection of the STL signal. It is demonstrated that by converting the conventional single-point scanning STL to the line scanning STL and employing suitable width of the time bins and the number of records, the imaging speed of the multi-channel averaging detection can be improved by a factor of 3.7 relative to the lock-in detection at the same signal-to-noise ratio of 6 dB and imaging resolution of 20 μm. Therefore, high-quality photothermal images of weakly absorbing defects can be recorded with higher efficiency and lower laser irradiance, making it possible to investigate large samples.
关键词： photothermal characterization,weakly absorbing defects,multi-channel averaging,Surface thermal lensing,optical materials
更新于2025-09-04 15:30:14