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 $3.5\mathrm{W}$ to $13.5\mathrm{W}$ . By operating the OPO under an optimized output coupling at $14\mathrm{W}$ of pump power, we obtain $>5\mathrm{W}$ of extracted signal power, more than 2.6 times that with a $\sim 5\%$ 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.