Nonlinear spectral broadening of a dual-carrier electro-optic frequency comb in a graphene oxide cladded silicon-rich nitride hybrid waveguide

We demonstrate a detailed theoretical analysis describing the generation of an electro-optic comb (EOC) in the near-IR range through discrete phase and amplitude modulation driven by radio frequency (RF) signal generators. Furthermore, the generated EOC spectra suffer nonlinear spectral broadening while propagating through a hybrid Si-rich nitride (SRN) waveguide structure integrated with two-dimensional (2D) layered graphene oxide (GO) films. We perform a detailed analysis to investigate the influence of GO layers, pump wavelength detuning, and other waveguide parameters on the evolution of comb spectra propagating through the hybrid waveguide structure. Owing to the strong modal overlapping between the SRN waveguides and the highly nonlinear GO films, the nonlinearity of the system is enhanced effectively, and broadband comb spectra have been achieved in the near-IR range. Furthermore, we investigate the spectral coherence of the generated comb spectra under different input conditions. The results exhibit strong potential to generate a tunable frequency comb with high spectral coherence in the near-IR range by employing the hybrid waveguide structure.