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.
Min Seok Jang (Tue,) studied this question.