摘要： 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 over coupled resonance regimes in 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 cavity is experimentally demonstrated at THz frequencies where the dynamic metasurface consists of metallic resonators embedded with thin film vanadium dioxide patches. By driving insulator to metal transition in vanadium dioxide, the THz optical response of the metasurface based cavity structure is modulated. The fabricated device exhibits perfect absorption modulation and reflection phase modulation up to 180°. The reported results demonstrate the potential of such structures for realizing novel devices such as tunable holograms, high-efficiency modulators and frequency tunable filters at THz. The analytical approach presented here can be applied for analysis and design of metasurface cavity structures based on other material systems at frequencies ranging from THz to mid-infrared.