During the propagation of array laser in the atmosphere, due to the influence of atmospheric coherence length, average wind velocity and laser duration, the beam quality in the far field will be reduced. In this paper, an array laser propagation model and a dynamic atmospheric turbulence phase screen are constructed. The peak intensity and the circumferential intensity are used as the criteria to evaluate the beam quality degradation of coherent and incoherent lasers in the far field. The results show that the beam quality of coherent combining is better than that of incoherent combining in a short laser duration; However, the beam quality of incoherent and coherent combination decreases and approaches gradually with the increase of laser duration. The researches can provide basic support for selecting the best beam combining mode when the high-power laser system is used in different environments.
This paper studied semiconductor parameters for the thermal effect of laser to the others quadrants when the millisecond-pulsed laser interacted with one quadrant of the Si-based p-i-n QPD. The thermal model and intrinsic carrier model were built on the basis of the semiconductor physics and thermal conduction theory, and a 3-D simulation model was built by the method of finite element, using COMSOL Multi-physics simulation software. It was taken into consideration that when the carrier was mainly derived from impurity ionization, the intrinsic carrier concentration is lower than impurity concentration at least an order of magnitude, it means that the concentration of intrinsic carrier is no more than 5×1014cm-3, and Si-Based semiconductor detector limit working temperature is 520K. The concentration distribution of intrinsic carrier and temperature distribution of all quadrants of QPD were simulated, and got rules which they changed over time. The conclusion was gotten, the thermal-induced failure time of the other quadrants of QPD decreased with the increase of laser energy density under the same laser spot. The thermal-induced failure time of the others quadrants of QPD extended with the increase of the lengths from every quadrant to the point of peak energy when the laser energy density was same. This paper provided important data basis for further research on the study of the interaction between laser and silicon-based semiconductor detectors.
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