Design of Si₃N₄ ridge-slot micro-ring resonator and generation of dual-comb based on orthogonally bicolor pumping

A novel high quality-factor (Q) micro-ring resonator (MRR) structure based on the Si₃N₄ ridge-slot waveguide is proposed, and the MRR is pumped by orthogonally polarized bicolor pumping to generate dual-comb. We optimized the structure of MRR by the finite element method and precise dispersion engineering, which finally obtained the suitable MRR geometry with negative dispersion characteristics at 1 550 nm, having Q of 1.7×10⁷ and the absorption loss as low as 2.6×10⁻⁵ dB/cm. The simulation model of generating dual-comb is established as coupled Lugiato-Lefever equation (LLE), which takes the higher order dispersion, cross-phase modulation (XPM), multiphoton absorption, and external pumping into account. Solved by the split-step Fourier method (SSFM) and the fourth-order Runge-Kutta (RK4) method, the numerical results show that the generated dual-comb is periodically equally spaced distribution, but with slightly different intensities in the time domain. In the frequency domain, there are 64 comb teeth with intensities higher than −100 dBm with a bandwidth of 120 nm. Particularly, in the case of bicolor orthogonal polarization pumping, a smaller amount of detuning does not greatly affect the bandwidth of the dual-comb.