Fig. 2. OPO characterization.

(A) Output FH power at the output lensed fiber versus on-chip FH power going into the waveguide SHG section. We begin to observe oscillation at ~50 mW going into the SHG section where the inset shows the optical spectrum analyzer (OSA; Yokogawa AQ6370D) trace of the oscillation. (B) Cavity transmission in the presence of parametric gain (see the Supplementary Materials). We collect the voltage output of the photodetector (PD) versus the input laser's wavelength to the cavity with a parametric gain introduced by a second laser. Inset shows transmission at different pump power levels around the wavelength of the FH light used to generate gain. Red is the cold cavity transmission, orange is the cavity transmission at gain/loss = 0.62, and blue is cavity transmission at gain/loss = 0.88. We estimate the gain/loss ratio based on the linewidth of the modes where they were 2.84, 2.73, and 0.9 pm for red, orange, and blue trace, respectively (see the Supplementary Materials). Sharp line on the left of the resonance corresponds to the beating of the two lasers.