Nanosecond AgGaS2 optical parametric oscillator with more than 4 micron output

This paper reports on a mid infra-red AgGaS2 optical parametric oscillator (OPO) pumped by nanosecond 1.064 micron Nd:YAG laser. Its wavelength tuning range is from 2.8 to more than 4.2 micron. Using singly resonating (SRO) configuration, the maximum absolute conversion efficiency obtained is about 10% (slope efficiency similar to 16%) which is equivalent to a pump depletion of 30-40%. A comparison is also made between the oscillation threshold of the single and double pump pass version of this SRO. In addition, the variation of the oscillation threshold with its output wavelength is also discussed.