Resonant optical tunneling-assisted Fano cavity with structured grating mirror

Abstract We propose a resonant optical tunneling-assisted Fano cavity enabled by a structured grating mirror, achieving highly tunable asymmetric spectral responses in mid-infrared range. The system leverages resonant tunneling through a prism-coupled multilayer with a bottom grating, where the narrow resonance supported by the structured grating mirror interfere with broadband tunneled transmission, giving rise to Fano resonance. Using rigorous coupled-wave analysis and full-wave simulations, we investigate the impact of grating parameters, air gap thickness, and incident angle on the resonance characteristics. The results demonstrate that the Fano resonance can be spectrally tuned and controlled by modifying structural and material properties, enabling applications in optical filtering and sensing. This work provides a pathway for engineering high-quality-factor all-dielectric resonant system with enhanced spectral selectivity and light–matter interactions.