A high numerical aperture, polarization-insensitive metalens for long-wavelength infrared imaging

In contrast to conventional bulk optical components, metasurface-based flat optical devices have shown excellent superiorities on manipulating polarization, phase, and amplitude of incident light. Specifically, flat metalenses play an essential role for applications in imaging and optoelectronic integration. Several metalenses operating at visible or near-infrared wavelengths have been recently demonstrated. However, flat optics for the long-wavelength infrared (LWIR) has received relatively less attention. Here, we demonstrate a polarization-insensitive, all-dielectric metalens operating at LWIR. The metalens has a numerical aperture of 0.6 at the wavelength λ = 10.6 μm. It can focus incident light down to a spot as small as ∼1.08λ and exhibits high-resolution imaging performance. In addition, because the metalens is fabricated by single step photolithography and CMOS-compatible processes, it is easy to realize high-throughput manufacture, which provides an efficient way for the development of compact optical devices for LWIR technology.