Spectral broadening and stimulated Raman conversion in a continuous-wave optical parametric oscillator

We have confirmed that single-frequency oscillation of a continuous-wave singly resonant optical parametric oscillator is limited to operation below a critical value of the pumping ratio, as predicted by early theoretical treatments. We also report different regimes of spectral broadening as well as stimulated Raman conversion of the signal wave above this critical pump level. We show that spectral broadening may be eliminated by implementing output coupling of the signal wave and demonstrate 8.6 W of total signal and idler output with single-frequency spectra at both wavelengths for 14.5 W of pump power.