A high energy end pumped Q-switched Nd:YAG laser

High energy Q-switched Nd:YAG laser has the characteristics of high peak power and narrow pulse width, which has been widely used in mass spectrometry, laser radar, laser indication and other fields. Compared with lamp pumped solid state lasers, laser diode pumped solid state lasers (all solid state lasers) have high optical-optical conversion efficiency and low waste heat generation rate, which greatly improve the reliability and environmental adaptability of the system and become a research hotspot for obtaining high-energy Q-switched Nd:YAG lasers. The end pumped all solid state laser can match the pumping beam with the laser oscillation mode, which is conducive to improving the beam quality and conversion efficiency of the laser. However, the high gain of the laser medium formed by the end pump is easy to cause self-excited oscillation, which greatly limits the improvement of the output energy of the Q-switched Nd:YAG laser. Therefore, restraining self-excited oscillation and improving the dynamic static ratio become the key technologies to obtain high energy end pumped all solid state Q-switched Nd:YAG laser. In order to obtain the 1064 nm Q-switched Nd:YAG laser output with high energy, high conversion efficiency and compact structure, based on the physical characteristics of the linear change of LD wavelength with temperature, this study changes the pump wavelength by adjusting the LD temperature to make it deviate from the absorption peak of the laser working material, and obtains effective control of the pump end gain, so as to achieve the suppression of self-excited oscillation. It is found that the LD energy and divergence angle have no obvious change with the temperature change, which provides a good precondition for LD wavelength optimization. The LD working temperature is optimized according to the dynamic static ratio and the output laser energy. Finally, the LD is selected to work at 30 ℃, and the corresponding LD wavelength is 797.5 nm, which deviates from the absorption peak of Nd:YAG crystal and is at an absorption wave valley. Finally, under the maximum pumping current of 170 A (20 Hz) for LD, the maximum output energy of Q-switched 1064nm laser is 95 mJ. The corresponding optical-optical conversion efficiency is 18%, and the dynamic static ratio of Q switching is 73%.