Yb:yag Sheet Intracavity Frequency Doubling Technology

Laser diode-pumped solid-state lasers(DPSSL, DPL) have been widely applied in basic research, material processing, medical treatment, military and, etc., due to their advantages, such as high efficiency, all solid-state construction, compactness, steadiness and long lifetime. And thin-disk laser, which allows realization of lasers with high output power, high efficiency, and good beam quality simultaneously, is one of the most important developing aspects of the DPSL. Thin-disk laser technology of Yb:YAG has been widely studied due to the needs of laser processing. In this paper, multi-passes pumped Yb:YAG thin-disk laser was studied, and with the system a good beam quality of high-repetition-rate 515nm green laser was achieved.In this paper, the theoretical model of multi-passes pumped thin-disk laser of Yb:YAG was analyzed, based on the model a 16-passes pump coupling system of thin-disk laser of Yb:YAG was built. Output power of the laser was estimated with the theoretical model, and the experimental study was carried out. At the pump power of 81.6W, when the reflector with the radius of curvature of-800mm and reflectivity of 95% was used,31.4W of the 1030nm laser was obtained, the optical-to-optical conversion efficiency was 38.5%; when the reflector with the radius of curvature of-2000mm and reflectivity of 90% was used,22W of the 1030nm laser was obtained, with M2≤1.1 at the optical-to-optical conversion efficiency of 27%.The equations of photon density and inverted population density about quasi-three-level with fast Q-switch were analyzed, with the rate equations. The absorption process of multi-passes pumped thin-disk laser of Yb:YAG was analyzed, an accurate description of the pump process was given. The inversion number of particles, pulse energy and pulse duration at a certain frequency of the continuous wave pumped thin-disk laser of Yb:YAG were simulated.Based on tne theory, the experiment was carried out, and the results were compared with the simulation.The rate equations of the intracavity frequency doubling about Yb:YAG was discussed. The non-critical phase matching about LBO of type I was analyzed, and the phase matching parameters were calculated. Through the ABCD matrix, a Z type cavity was designed, a good pattern matching was achieved, and the waist radius of frequency doubling in the crystal was controlled. At the pump power of 81.5W, with the repetition rate of 5kHz, a 10.2W 515nm green laser was obtained, with M2x of 1.3, M2y of 1.6 at the optical-to-optical conversion efficiency of 12.5%.The pulse duration was 150ns.At last, a few ideas combining with the practice for the later work were put forward.