Optical Parametric Oscillator with Adjustable Pulse Width Based on KTiOAsO4

A type II non-critically phase-matched KTiOAsO4 (KTA) optical parametric oscillator (OPO) was pumped by a 1064 nm laser with an adjustable output pulse width. This enabled the generation of signal and idler outputs with variable pulse width. When the pulse width of the 1064 nm pump field was varied in the range 5.7-12.6 ns, the corresponding pulse widths of the 1538 nm (signal) and 3468 nm (idler) fields varied in the ranges 5.7-7.9 ns and 7.1-19.7 ns respectively. Under a pulse repetition rate of 20 Hz, maximum output pulse energies of 0.44 mJ at 3468 nm and 1.135 mJ at 1538 nm were obtained for a pump energy of 8.8 mJ. The maximum optical-optical conversion efficiency (pump to combined signal and idler) of this system was 17.9%, and the maximum slope efficiency was 50.7%.