A Reflective Metalens With Tunable Focal Length for Millimeter Waves

Abstract

A novel architecture of reconfigurable, flat metalens is proposed with an electrically tunable focal length for applications in wireless communication systems working at the frequencies of millimeter waves (i.e., 60 GHz). In this approach, a reflective metalens made of silicon bricks is distributed on a grounded multilayer hosting films of a phase-transition material, namely, vanadium dioxide. The multilayer, acting as a ground plane with a controllable position, provides different phase profiles in the same metalens and, therefore, different focal lengths. Our numerical investigation of thermal and electromagnetic effects shows that the metasurface can reversibly tune the focal length at 27, 31, and 33 mm. In addition, in the operating frequency range between 58 and 62 GHz, the tunability of the metalens remains unaltered. Dynamically controlling the focal point of millimeter waves is highly desirable in wireless communications, especially for 5G and 6G cellular systems applications.INDEX TERMS Millimeter waves, Tunable and active metasurfaces, Reconfigurable devices, Reflective metalens, Vanadium dioxide.