Multiple-wavelength quasi-phase-matching for efficient idler generation in MgO:LiNbO3 based nanosecond optical...

We present numerical results for optimization of the overall idler conversion efficiency of a nanosecond optical parametric oscillator (OPO), wherein the signal generated in the OPO process is also used as the pump for a difference frequency generation (DFG) process in a quasi-periodic MgO:LiNbO(3) crystal. The phase-matching conditions are considered such that the generated idler frequencies in both the processes (i.e., OPO and DFG) coincide. Optimization for the idler generation has been performed with respect to the different parameters, such as input pump power, pump pulse duration, and the output coupler reflectivity, for quasi-phase-matched interaction in MgO:LiNbO(3). Wavelength of the pump, signal, and idler waves considered in the optimization are 1.064 μm, 1.456 μm, and 3.95 μm, respectively. A maximum overall idler generation efficiency of ≈33% could be obtained in the simultaneous OPO+DFG process for a pump pulse duration of 72 ns and output coupler reflectivity (R(s)) of 90%, whereas for the stand-alone OPO process, the maximum idler generation efficiency was found to be ≈15%. The optimization has been illustrated for an average pump power of 8 W at a pulse repetition frequency (PRF) of 10 kHz. This approach of simultaneous OPO+DFG process can be employed to significantly enhance the idler generation efficiency of nanosecond OPOs.