Fig. 2: Near-IR to mid-IR frequency combs from nanophotonic OPOs on a single chip.

a Schematic of the experimental setup used to pump and measure the synchronously pumped optical parametric oscillator chip. The image of the OPO chip is shown alongside, b Experimental measurements of the spectral and temporal characteristics (intensity auto-correlation trace) of the electro-optic pulsed pump showing a pulse-width of ~1 ps, c Broadband infrared spectral coverage of the OPO chip showing the signal and the idler spectrum as its operation is tuned from degeneracy to far non-degeneracy. Separate colors represent outputs from different OPO devices on the same chip with distinct poling periods. Zoomed-in versions display the underlying comb line structure of the power spectrum envelope of the signal and idler combs. The top panel represents the fine-tuning range of the corresponding OPO spectrum obtained by pump wavelength tuning. The dashed line indicates the tuning range for each OPO (assuming 30 nm of pump tuning). Filled dots represent measured data, while empty dots indicate inferred spectrum from its signal/idler counterpart. (Detailed spectrum for the tuning results are presented in Fig. 3c and Supplementary Section 14).