Tunable multi-channel optical filter based on the near-infrared ultralow-loss phase change material Sb₂Se₃

Chalcogenide phase-change material (Ge₂Sb₂Te₅) has attracted considerable research interest in recent years for tunable structural color applications, owing to its pronounced contrast in optical properties between amorphous and crystalline states. However, the strong absorption of conventional Ge₂Sb₂Te₅ has significantly limited its applicability in the near-infrared (NIR) wavelength range. Herein, we utilize the near-zero absorption characteristic of the emerging phase-change material Sb₂Se₃ in the NIR band to construct a Fabry-Pérot cavity structure. This structure not only enables resonance peaks with high transmittance and large modulation range, but also allows a multi-channel filter to be achieved by increasing the thickness of Sb₂Se₃. This tunable multi-channel spectrally selective filter presents significant application potential in advanced fields such as multi-gas sensing, laser beam combining, and adaptive multi-spectral imaging.