Fig. 1. The meta-atoms of metalens：（a） Schematic diagram of designed meta-atoms； （b） The relationship between propagation phase and radius of meta-atoms in LWIR； （c） The transmission spectrum of meta-atoms in LWIR； （d） The electric field distribution of meta-atoms at wavelength of 9-11.5 μm

Fig. 2. The simulation results of metalens in 1 mm diameter：（a-c） Simulated focusing effect at the operating wavelength of the 9，10 and 10.5 μm for a metalens with a central wavelength of 10.5 μm； （d-f） Comparison of the surface phase distribution of the metalens at 9，10 and 10.5 μm. The dot plots are the theoretical surface phase distribution of the metalens with different operating wavelengths，and the error bar shows the deviation of the actual phase distribution

Fig. 3. The fabrication of metalens：（a） Fabrication process flow diagram of the metalens； （b） Local view of the fabricated metalens； （c） Photograph of the fabricated metalens； （d） Full view of the surface of the metalens

Fig. 4. Focusing performance test of the fabricated LWIR metalens：（a） Index path of experiment； （b） Simulation intensity of the focal plane； （c） Measured power intensity across the focal plane； （d） Intensity fitting of the focal spot. The original data are taken from （c）；（e） Image of the focal spot along the axis of the metalens

Fig. 5. Metalens imaging experiment results：（a） Photograph of monitor； （b） Photograph of face； （c） Photograph of hands； （d） Photograph of fire