Fano-Like Resonances in Coupled Sagnac Interferometers Formed by a Self-Coupled Waveguide

Abstract

We demonstrate Fano-like resonances in silicon-on-insulator (SOI) nanowire-based coupled Sagnac interferometers (SIs) formed by a self-coupled waveguide. By adjusting the reflectivity of the two SIs and coupling strength between them, we tailor coherent mode interference to achieve high-performance optical analogues of Fano resonance. The device is theoretically analyzed and experimentally fabricated on a SOI platform. Theoretical analysis predicts periodic Fano-like resonances with a high extinction ratio and a steep slope rate, arising from strong coherent optical mode interference within a compact resonator comprising two SIs and a connected feedback waveguide. Experimental results align with the theoretical model, validating the expected resonance behavior and confirming the effectiveness of the design. These findings underscore the potential of compact coupled SIs for generating Fano-like resonances, enabling broader applications in integrated photonics.