Study Of High-power Diode-pumped Laser Module Features

Diode-pumped solid-state laser (DPSSL, DPL) with the advantages of high efficiency, compact structure, stability, long life and all-solid, has been widely used in the material processing, military, medical, scientific and other fields, and has become a hot spot of novel solid-state laser development worldwide. Thermal effect of Solid-state laser has been an important research topic in laser technology. Especially in the high-power pumping, the thermal effect seriously degrades the beam quality. The main beam-quality degradation factors are birefringence-induced bifocusing and thermally induced wavefront (WF) deformation. Wavefront aberration mainly includes spherical aberration and higher-order aberrations. In this thesis, a series of theoretical and experimental researches on thermally-induced birefringence and wavefront (WF) deformation were studied.The theoretical model of thermally-induced thermal lensing and spherical aberration of high-power diode-pumped rod Nd: YAG laser module was established. It was obtained the relationship between the thermally-induced thermal lensing and spherical aberration with various changing factors, providing the theoretical reference for research on thermal effect of laser module. The experimental research on thermally-induced spherical aberration of laser module was developed. Thermally-induced spherical aberration of repeat pulse Nd:YAG laser module was measured and compensated, providing the experimental reference to the laser with high power and high beam quality. The effect of the performance parameters of side-pumped repeat pulse Nd:YAG laser module on generated laser was studied, providing the foundation for evaluating the performance of laser module.Basic theory of thermal effect of diode-pumped laser and the development of compensation for thermal effect around the world was introduced, with emphasis on the compensation method of thermally-induced birefringence, bifocusing, spherical aberration and high order aberrations.Thermal lensing and spherical aberration of side-pumped high-power diode Nd: YAG laser module was theoretically analyzed and numerically simulated. It was achieved the heat distribution of gain crystal profile, the relationship between pumping inhomogeneityδand thermal lensing length as well as spherical aberration, the relationship between pumping power as well as crystal length and spherical aberration, and the relationship between laser crystal physics parameters and thermal lensing length as well as spherical aberration.Measurement theory, system and experimental result of spherical aberration of repeat pulse Nd:YAG laser module was introduced in this thesis. Meanwhile, the change between spherical aberration and crystal cooling temperature was analyzed. Compensation theory and experiment of spherical aberration was described in detail. Moreover, the change between spherical aberration and operating current in the changes of compensation was analyzed, Finally, the influence of spherical aberration on beam quality factorβwas summarized. A fine accomplishment was achieved by the experimental study on the effect of spherical aberration compensator in MOPA system.Furthermore, considering the output power and beam quality of the laser module in resnator and as an amplifier, the effect of the performance parameters of side-pumped repeat pulse Nd:YAG laser module on generated laser was studied.