Research On High-Power Ld Pumped Intracavity Frequency-Doubled Nd:YAG Laser

Laser diode-pumped solid-state lasers (DPSSL, or DPL) have become a developing focus of novel solid-state lasers and have wide applications in material processing, military, medical therapeutics, and basic research, etc., due to their advantages, such as high efficiency, compactness, steadiness, long lifetime and all solid-state construction. High-power all solid-state lasers are becoming mainstream lasers, and high-power LD pumped green laser has become the researching emphasis because its potential application in material processing, laser isolation of uranium isotopes, etc. This dissertation has made systematically theoretical and experimental research on the high-power, high repetition rates all solid-state intracavity frequency-doubled Nd:YAG laser. When the pumping current was 17.3 A, a green power of 82 W with 20.4 kHz repetition rate and 230 ns pulse width was generated. In fact, an output power of 85 W was obtained by multiplying a 1.04 corrected factor of power meter. The output power instability was (1.03% and optical-optical conversion efficiency 9.7%. The mainly innovation points can be summarized as follows1. Double Q-switch intracavity synchronizing modulation technology was adopted with adjusting the deflection angle of Q-switches, and the oscillation of fundamental wave was effectively suppressed. The peak power density of intracavity fundamental wave increased, and a foundation of high frequency doubling efficiency was made. A green laser output power of 85 W was obtained with nearly Gaussian distribution and fine quality, which is the lead in mainland, advanced in the international range.2. The influence of the KTP's temperature distribution on the frequency doubling efficiency was calculated, and so did for the deviation of the optimum phase matching angle due to the increasing of KTP's temperature. In experiments, rotating crystal, strengthened chilling, controlling the spot size of laser in the KTP was used simultaneously. The influence of KTP's thermal effect was controlled and the efficiency of the frequency doubling increased. The steady working of KTP crystal in high power level was realized.3. A traditional plano-concave cavity was used. The influence of the thermal lens and thermal induced birefringence of the Nd:YAG rod in high power pumping level was analyzed, and we found high power laser operated in the second stable region and the fundamental mode volume was restrained. On the basis of calculations and experiments, the mode volume increased and the spot size of fundamental wave in the KTP was stable in a certainly changing range of pumping power. A single direction green laser output power of 85 W with (1.03% power instability was acquired on the condition of single Nd:YAG rod. Up to now, more than 90 W of green laser output power was obtained. In the short future, more than 100 W would be realized by using suitable resonator, more excellent nonlinear crystal and more effective controlling step of thermal effects.