Simultaneous dual-wavelength nanosecond mid-infrared optical parametric oscillator

An optical parametric oscillator (OPO) simultaneously generating dual-wavelength mid-IR radiation at 3295 and 3469 nm was demonstrated in this paper. In an extremely low-loss singly resonant OPO for the signal wave, two OPO crystals, KTA and KTP, were placed coaxially in the resonator with their Y axes perpendicular to each other. So the different polarization component of the 1064 nm fundamental wave from one Nd:YAG laser could separately pump the two OPO crystals, constructing a parallel stacked OPO scheme. Simultaneous dual-wavelength operation at the idler wavelengths of 3295 and 3469 nm were obtained, with the maximum average powers being 1.01 and 0.81 W, respectively. The achieved minimum pulse width was 6.2 ns for the two wavelengths, producing pulse peak powers of 23.3 and 18.7 kW for 3295 and 3469 nm, respectively. The wavelength designability and power scalability makes the parallel stacked OPO a promising multi-wavelength mid-infrared laser source for high speed differential absorption lidars.