Sub-nanosecond passively Q-switched Yb : YAG/Cr4+: YAG sandwiched microchip laser

摘要

We report on laser-diode pumped low-threshold, and compact passively Q-switched Yb:YAG microchip lasers, with Cr4+:YAG crystals as the saturable absorbers. The laser threshold at the fundamental wavelength of 1.03 mu m is as low as 0.25 W, and the slope efficiency is as high as 36.8%, and the optical-to-optical efficiency is as high as 27% for the 95% initial transmission of the Cr4+:YAG crystal. A pulse width of 1.35 ns and peak power of over 8.2 kW was obtained. Using a 5 mm thick KTP crystal as the second-harmonic generation medium, 514.7 nm green light of 155 mW power was generated. The pulse duration of 480 ps was generated at 1.03 mu m by using 85% of the initial transmission of the Cr4+:YAG saturable absorber. Stable single-longitudinal-mode oscillation and wide-separated multi-longitudinal-mode oscillation due to the etalon effect of the Cr4+:YAG thin plate was achieved at different pump power levels.