Studies of the output efficiency of signal wave as a function of reflectance of output coupler in nanosecond single-resonant optical parametric oscillators

We investigated the output efficiency of signal wave as a function of reflectance of output coupler in nanosecond optical parametric oscillators. The measurements are performed for a type-I critically phase matched signal-resonant optical parametric oscillator of Beta-Barium-Borate crystal. It is observed that the threshold fluence and slope efficiency increases as the reflectance of output coupler decreases, resulting that the maximum efficiency of the signal output was achieved with ~ 60% reflectance of output coupler. It is found that the experimental result of output characteristics is in good agreement with the numerical prediction by a simple numerical model.