High Repetition Rate, TEM00 Mode, Compact Sub-Nanosecond 532 nm Laser

As a critical transmitter, compact 532 nm lasers operating on high repetition and short pulse widths have been used widely for airborne or space-borne laser active remote sensing. We developed a free space pumped TEM00 mode sub-nanosecond 532 nm laser that occupied a volume of less than 125 mm x 50 mm x 40 mm (0.25 L). The fundamental 1064 nm laser consists of a passively Q-switched composite crystal microchip laser and an off-axis, two-pass power amplifier. The pump sources were two single-emitter semiconductor laser diodes (LD) with 808 nm wavelengths and a maximum continuous wave (CW) power of 10 W each. The average power of the fundamental 1064 nm laser was 1.26 W, with the laser operating at 16 kHz repetition rates and 857 ps pulse widths. Since the beam distortion would be severe in microchip lasers due to the increase in heat load, in order to obtain a high beam quality of 532 nm, the beam distortion in our experiment amplifying the fundamental laser was compensated by adjusting the distribution of the pumping beam. Furthermore, in the critical phase matching (CPM) regime for the second harmonic generation (SHG), a Type I LiB3O5 (LBO) crystal obtained 770 ps, a beam quality of M-2 < 1.2, and a 16 kHz pulse output at 532 nm, which was better than 0.6 W average power.