Design of a Graphene-Enabled Dual-Mode Kerr Frequency Comb

On-chip Kerr frequency combs open up unprecedented opportunities for developing compact, low-cost, and high-density wavelength-division multiplexing (WDM) techniques for optical communications and optical interconnects. However, to achieve high-density WDM channels, a large-radius microring could be used to develop a Kerr frequency comb with a small free spectral range (FSR), inevitably increasing the comb's footprint and threshold. Herein, we theoretically study a dual-mode Kerr frequency comb based on a graphene-on-silicon (GOS) microring to overcome the limitation. Theoretical results show that a TE
₀
-mode comb with a 50-dB bandwidth of 200 nm and FSR of 170 GHz, and a TE
₁
-mode comb with a 50-dB bandwidth of 130 nm and FSR of 212.4 GHz could be generated in the single GOS microring. Moreover, the TE
₀
-mode and TE
₁
-mode combs could be selectively activated via modulating the Fermi level of the graphene nanoribbons integrated on the silicon microring. The study is expected to provide a useful technique for developing on-chip coherent light sources for high-speed optical communications.