Fig. 1. Database of all-As₂Se₃ microstructure units designed for the 9–11 µm wavelength range. (a) Ideal phase profile of a broadband achromatic metalens for wavelengths λ = 9 µm, 10 µm, 11 µm. (b), (c) Microstructure unit. (d) Dispersion compensation ability of microstructure unit database with a height of 11 µm. (e) Dispersion compensation ability of the microstructure unit database with a height of 8 µm.

Fig. 2. Design and focusing performance of an LWIR broadband achromatic all-As₂Se₃ metalens. (a) Schematic diagram illustrating achromatic focusing. (b) Designed achromatic metalens and an expanded view of the microstructure arrays in the marked area. (c) Intensity profiles of the achromatic metalens along axial planes at various incident wavelengths. (d) Intensity profiles of the chromatic metalens without PSO algorithm optimization.

Fig. 3. Design and dynamic coaxial focusing performance of an LWIR broadband achromatic all-As₂Se₃ metalens. (a) Schematic diagram demonstrating dynamic tunable coaxial focusing. (b) Designed achromatic metalens with an expanded view of the microstructure arrays in the marked area. (c) Intensity evolution of each focusing state along the z-axis.

Fig. 4. Design and dynamic off-axial focusing performance of an LWIR broadband achromatic all-As₂Se₃ metalens. (a) Schematic diagram demonstrating the dynamic off-axial focusing. (b) Designed achromatic metalens with an expanded view of the microstructure arrays in the marked area. (c) Intensity evolution of each focusing state along the z-axis.