Plasmonics has established itself as a branch of physics which promises to revolutionize data processing, improve photovoltaics, and increase sensitivity of bio-detection. A widespread use of plasmonic devices is notably hindered by high losses and the absence of stable and inexpensive metal films suitable for plasmonic applications. To this end, there has been a continuous search for alternative plasmonic materials that are also compatible with complementary metal oxide semiconductor technology. Here we show that copper and silver protected by graphene are viable candidates. Copper films covered with one to a few graphene layers show excellent plasmonic characteristics. They can be used to fabricate plasmonic devices and survive for at least a year, even in wet and corroding conditions. As a proof of concept, we use the graphene-protected copper to demonstrate dielectric loaded plasmonic waveguides and test sensitivity of surface plasmon resonances. Our results are likely to initiate wide use of graphene-protected plasmonics.

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 we demonstrate a solid state supercapacitor effect with the high-k dielectric hafnium oxide that allows modulation from the near-infrared to shorter wavelengths close to the visible spectrum with remarkably low voltages (~3 V).The electro-absorption modulators are based on a Fabry-Perot resonator geometry that allows modulation depths over 30% for free-space beams.

Abstract:We demonstrate a graphene-based electro-absorption modulator with extremely small modulation volume that can be controlled by low gating voltages 1-3 V and shows light modulation at wavelengths as short as 900 nm. Our choice of hafnium oxide dielectric separator gives the possibility to obtain significant electro-optical effect in a simple optical heterostructure. Having low power consumption, our devices could find a wide range of applications in telecom industry.

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