Enhancing antireflection with symmetry-engineered Kerker effect

With significant advances in mid-wave infrared (MWIR) photonics, reducing unwanted reflections is critical for MWIR devices. Recently, multi-resonant metasurfaces have emerged as a potentially attractive platform for broadband antireflection (AR) across the solar spectrum. Unfortunately, such metasurfaces provide only a restricted AR efficiency in a broader MWIR range. Here, we show that broadband AR can be enabled by leveraging the generalized Kerker effect on a judiciously designed elliptical Si metasurface. It is argued that the generalized Kerker effect can be maximized by suppressing the near-field coupling between Mie resonators and controlling the symmetry of resonators. With this understanding, we can achieve broadband AR with more freedom by engineering symmetry rather than physical dimensions. We demonstrate the value of our optimized metasurface by showing 1.9% averaged reflectance in the 2.5−6 μm spectral range. This work opens up new design strategies for antireflective nanophotonic structures applicable to high-performance MWIR devices.