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

Abstract

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 μm 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 μm 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 Cr 4+:YAG thin plate was achieved at different pump power levels. © Springer-Verlag 2006.