Subvolt high-speed free-space modulator with electro-optic metasurface

Active metasurfaces incorporating electro-optic (EO) materials enable high-speed free-space optical modulators that show great promise for a wide range of emerging applications, including free-space optical communication, light detection and ranging, and optical computing. However, the limited light-matter interaction lengths in ultrathin metasurfaces typically require high driving voltages exceeding tens of volts. Here we present ultralow-voltage, high-speed free-space optical modulators based on silicon-organic-hybrid metasurfaces with dimerized-grating-based nanostructures. By exploiting a high-Q quasi-bound state in the continuum, normally incident light is effectively trapped within a submicrometer-scale silicon slot region embedded with organic EO material. Consequently, highly efficient modulation is obtained, enabling data transmission at 50 Mbps and 1.6 Gbps with driving voltages of only 0.2 V and 1 V, respectively. These unprecedented metasurface modulators operating at complementary metal-oxide-semiconductor (CMOS)-compatible voltage levels provide the pathway toward energy-efficient high-speed active metasurface devices.