Solid-State Electrolyte-Gated Graphene in Optical Modulators.

The gate-tunable wide-band absorption of graphene makes it suitable for light modulation from terahertz to visible light. The realization of graphene-based modulators, however, faces challenges connected with graphene's low absorption and the high electric fields necessary to change graphene's optical conductivity. Here, a solid-state supercapacitor effect with the high-k dielectric hafnium oxide is demonstrated that allows modulation from the near-infrared to shorter wavelengths close to the visible spectrum with remarkably low voltages (≈3 V). The electroabsorption modulators are based on a Fabry-Perot-resonator geometry that allows modulation depths over 30% for free-space beams.