Interferometric output coupling of ring optical oscillators

We demonstrate the successful deployment of an antiresonant ring (ARR) interferometer within a ring optical resonator and its use for absolute optimization of output power. The integration of the ARR interferometer in a folded arm of the ring oscillator provides continuously variable output coupling over broad spectral range and under any operating conditions. We demonstrate the technique using a picosecond optical parametric oscillator (OPO), where we show continuously adjustable output coupling and optimization of the output power for different pump power conditions, from 3.5 W to 13.5 W. By operating the OPO under an optimized output coupling at 14 W of pump power, we obtain >5 W of extracted signal power, more than 2.6 times that with a ~5% conventional output coupler. We also show that the inclusion of the ARR interferometer has no detrimental effect on the spatial, temporal, and spectral characteristics of OPO output.