Dynamic-Metasurface-Based Cavity Structures for Enhanced Absorption and Phase Modulation

Metasurface-based optical cavity structures consist of a metallic metasurface realized on top of a dielectric slab backed with a metal plane. Such structures have been employed in the design of optical devices such as flat lenses, wave plates, and holograms at frequencies from microwave to mid-infrared. Recently, such structures with dynamically reconfigurable optical characteristics have been explored for electrically tunable optical absorption and reflection phase modulation. To date, absorption modulation and phase modulation have been realized with large insertion loss. In this work, we employ an analytical approach based on transmission line theory where the metasurface is represented by a surface admittance. We extend the above approach for the design and analysis of under- and overcoupled resonance regimes in the metasurface cavity structure. This enables a mutual design of cavity thickness and individual metasurface for large amplitude or phase modulation. A dynamic-metasurface-based optical cavit...