Near-Infrared Super-Absorbing All-Dielectric Metasurface Based on Single-Layer Germanium Nanostructures

摘要

Strong near-infrared absorption in ultrathin semiconductor layers is essential for increasing the speed and efficiency of photocarrier extraction in optoelectronic devices. However, the absorption of a free-standing ultrathin film can never exceed 50% in principle. In this article, an all-dielectric germanium metasurface absorber in the near-infrared region (800-1600 nm) is proposed theoretically and experimentally. Near-unity absorption can be achieved in such a subwavelength-thin (approximate to 0.13 lambda(0)) layer of nanostructures based on the destructive interference between simultaneously excited electric and magnetic dipoles inside each element in the backward direction in combination with the destructive interference between the scattered field and the incident field in the forward direction. Its response is both polarization-independent and angle-insensitive, with over 80% absorption at an incident angle up to 28 degrees. This ultrathin and flexible design paves the way for realizing next generation optoelectronic devices aimed for high-speed photon detection and energy harvesting.