Fig. 7.

Experimental results for a Si₃N₄ microring with width of 1750 nm ± 10 nm and height of 623 nm ± 2 nm. (a) Pump transmission for the input power of 120 mW ± 15 mW, measured by the DAQ at a pump tuning speed of − 100 GHz/s. (b) Comb spectrum corresponding to the soliton step with the pump detuning marked by the vertical arrow in (a). The inset shows the measured resonance dispersion (red dots) versus a quadratic fit (blue solid line), from which D₂/2π = 53 MHz ± 2 MHz is extracted. (c) Beat-note measurement for the comb line near 1539 nm (marked by red circle in the spectrum in (b)). In (b) and (c), a power of 0 dB is referenced to 1 mW. The spectrum in (b) includes output fiber coupling loss (≈ 6 dB at the pump wavelength).