(a) Schematic of the optical modes of the ring resonator coupled to a straight waveguide at the DW and pump frequencies. (b) Coupling quality factor Qc (blue, left y-axis) and ring/waveguide mode overlap Γ at the coupling point (red, right y-axis), for R = 23.3 μm, RW = 1600 nm, W = 550 nm, and G = 700 nm. (c) Simulated intracavity comb spectrum. The variation in Qc in (b) indicates that high frequency comb components will not be well extracted, as shown through the extraction efficiency η assuming Qi = 3 × 106 (green).