Extended Data Fig. 3: Transmission spectrum of a 2D device across three FSRs.

Measured transmission spectrum in the pump, signal and idler FSRs, corresponding to Fig. 2. ∆ν is the frequency relative to the longitudinal mode resonance, and Ω is the FSR. The shape of the transmission spectrum in these FSRs is almost identical. The small variation in the overall transmission across bands is mainly because of the frequency response of the grating couplers.