DETERMINATION OF OPTIMUM REFLECTANCE OF OUTPUT COUPLER IN NANOSECOND SINGLY-RESONANT OPTICAL PARAMETRIC OSCILLATOR

We investigated the signal output efficiency of a singly-resonant ns-optical parametric oscillator based on LiNbO3 with the double-pass pump as a function of reflectance (R) of the output coupler. The measured signal output exhibited a broad maximum around R ~ 35% at a fixed pump energy of 100 mJ/pulse, yielding a maximum signal output efficiency of ~ 38%. The experimental results were well-supported by the numerical calculation using a split-step beam propagation model. We also found that the same beam propagation model with one-dimensional diffraction predicts nearly the same results, enabling fast numerical determination of the optimum reflectance of the output coupler.