Guided-mode resonant grating filter based on Sb2Se3 with dual-band tuning

Tunable optical filters show excellent performance in integrated optics. Present schemes for tunable filter either have a large footprint or suffer from mediocre performance, hindering the development of integrated optics systems. Here, a tunable guided-mode resonant grating filter is elaborately designed through a precise, modified coupling mode theory. This structure consists of a silver metallic grating and a multilayer waveguide. The grating period of the grating layer is arranged in a gradient descent configuration. The diffraction effects produced by the grating structure, when coupled with the guided modes in the underlying multilayer waveguide, result in guided-mode resonance, thereby achieving band-pass filtering. We employ Sb2Se3, a phase-change material, as the dielectric layer in the multilayer waveguide structure. By controlling the temperature, Sb2Se3 can transition between amorphous and crystalline states, enabling switching between two operational bands. Simulation results demonstrate that the transition between the amorphous and crystalline states of Sb2Se3 allows for switching of the filtering range from 1262.5-1269.5 nm to 1544-1552 nm. We analyzed the electric field energy distribution and the quality factor (Q) of the resonance peaks to verify and understand the device's performance. Our design offers a novel approach to achieving tunable filtering in the near-infrared band, with potential applications in signal processing, wireless communication, and the medical field.