Picosecond laser system based on microchip oscillator seed

A compact near-diffraction-limited picosecond microchip oscillator-amplifier system was developed. When pumped by 0.9-W average power pulsed radiation, the microchip generated 9-mu J energy pulses of 400-ps duration at 1-kHz rate, in a nearly TEM(00) transversal mode (beam quality factor, M(2) < 1.1). The microchip Output was amplified up to 12-mJ pulse-energy at 1-10 Hz repetition rate in a two-pass flash-pumped Nd:YAG amplifier. We used the 1064-nm output beam for nonlinear conversion to 532-nm second harmonic (SH) and 266-nm fourth harmonic (FH). The pulse-energy of SH and FH output was 6-mJ and 1.6-mJ, respectively, which corresponds to 50 % and 13 % conversion efficiency.