Numerical Investigation of on-Chip Multi-Gas Sensing Using a Low-Repetition-Frequency Microcavity Kerr Comb With Backward Interference Structure

By integrating a microcavity Kerr frequency comb with an interferometric arm structure for backward coupling with a slot sensing waveguide, we present a new on-chip multi-gas sensing device. The microcavity used for frequency comb generation has a novel symmetric double-ring structure with a large roundtrip length, which makes it possible to obtain high-resolution frequency-resolved absorption spectra. In the meanwhile, a flat octave-spanning broadband spectrum is obtained by dispersion engineering of the Si ₃ N ₄ -based micro-rings with a horizontal single slot structure. Without the use of an additional gas cell, the large-length sensing waveguide allows for improved integration. A multiple soliton comb with high pump-to-frequency comb conversion efficiency under the optimization of the microcavity structure to improve pump depletion was obtained. The simulation shows its high stability and application feasibility, and the sensing performance of several gas species in different wavelength regions is verified and analyzed.