We report a broadband electro-optical (EO) modulator based on tunable plasmonic metamaterial. Transparent conducting oxides provide an excellent active plasmonic material for optoelectronic applications. By utilizing our indium-tin-oxide- (ITO) based multilayer structure, light absorption of the active ITO layer can be electrically modulated over a large spectrum range. Based on the attenuated total reflectance configuration, bias polarity-dependent modulation up to 37% has been experimentally demonstrated. This EO modulator has advantages of simple design, easy fabrication, compact size, broadband performance, large modulation depth, as well as compatibility with existing silicon photonics platforms.

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We demonstrate greatly enhanced light absorption by monolayer graphene over a broad spectral range, from visible to near IR, based on the attenuated total reflection. In the experiment, graphene is sandwiched between two dielectric media referred to as superstrate and substrate. Based on numerical calculation and experimental results, the closer the refractive indices of the superstrate and the substrate are, the higher the absorption of graphene is. The light absorption of monolayer graphene up to 42.7% is experimentally achieved.