Incident-angle-independent tuning of graphene-enhanced Fano resonances using loss modulation

Tunable Fano resonances enable strong and spectrally selective mid-infrared (MIR) absorption, offering opportunities for advanced detection and sensing. However, their pronounced dependence on the incidence angle limits practical use in scenarios where illumination is uncontrolled. We propose an angle-insensitive and dynamically reconfigurable MIR absorber obtained by integrating a graphene sheet with an all-dielectric Fano metasurface. Using coupled-mode theory, we quantify how electrically tunable graphene losses reshape the Fano linewidth and modify the balance between radiative and absorptive channels. Full-wave simulations show that the device is almost entirely insensitive to incident angle, while maintaining narrow linewidth and tunability. These results demonstrate a viable route toward angle-insensitive and reconfigurable MIR absorbers, with potential impact in infrared imaging and environmental or chemical sensing.