Dynamic phase-only modulation with transmissive metasurfaces

In this presentation, we discuss two important topics in the field of active metasurface. The first topic is achieving independent phase and amplitude modulation in transmissive metasurfaces. We present a systematic approach to achieving phase-only modulation by leveraging a single optical resonance. We theoretically demonstrate that the upper bound of transmittance for single-resonance phase-only modulation is 25%, which we validate with a Ge/LNO metasurface achieving near 2π electro-optic phase modulation with 22% transmittance. In the second part, we present our recent experimental work on active beam-switching metasurfaces operating with only a single global gate bias, instead of using numerous independently-addressable local gate electrodes. We then theoretically expand the idea of single-gate beam switching from two-level to multi-level configurations by utilizing a low-loss dielectric metasurface platform with freeform inverse-design approaches.