Reconfigurable all-dielectric metalens with diffraction-limited performance
Mikhail Y. Shalaginov, Sensong An, Yifei Zhang, Fan Yang, Peter Su, Vladimir Liberman, Jeffrey B. Chou, Christopher Roberts, Myungkoo Kang, Carlos Rı́os, Qingyang Du, Clayton Fowler, Anu Agarwal, Kathleen A. Richardson, Clara Rivero‐Baleine, Hualiang Zhang, Juejun Hu, Tian Gu
Abstract
Active metasurfaces, whose optical properties can be modulated post-fabrication, have emerged as an intensively explored field in recent years. The efforts to date, however, still face major performance limitations in tuning range, optical quality, and efficiency, especially for non-mechanical actuation mechanisms. In this paper, we introduce an active metasurface platform combining phase tuning in the full 2π range and diffraction-limited performance using an all-dielectric, low-loss architecture based on optical phase change materials (O-PCMs). We present a generic design principle enabling binary switching of metasurfaces between arbitrary phase profiles and propose a new figure-of-merit (FOM) tailored for reconfigurable meta-optics. We implement the approach to realize a high-performance varifocal metalens operating at 5.2 μm wavelength. The reconfigurable metalens features a record large switching contrast ratio of 29.5 dB. We further validate aberration-free and multi-depth imaging using the metalens, which represents a key experimental demonstration of a non-mechanical tunable metalens with diffraction-limited performance.