Graphene has unique and advantageous electronic and optical properties, especially in the underdeveloped terahertz range of the electromagnetic spectrum. Sub-micron graphene structures support terahertz (THz) plasmonic resonances that can be tuned by applying a gate voltage. Because these plasmonic structures are sub-wavelength in size, they need to be integrated with a THz antenna or a metamaterial structure to optimize the graphene coupling to the free space radiation. Furthermore, nearly all THz optoelectronic applications including detectors, filters, and modulators require electrical connection or antenna coupling to the graphene, which inhibits the accumulation of charge at the edges of the graphene. Here, we present the first observation and systematic study of plasmon resonances in a hybrid graphene-metal design in which the graphene acts as a gate-tuneable inductor, and metal as a capacitive reservoir for charge accumulation. We experimentally demonstrate a large resonant absorption in low-mobility graphene ( cm V s ), and show that the peak can approach 100% in an optimized device, ideal for graphene-based THz detectors. We predict that use of high mobility graphene ( cm V s ) will allow resonant THz transmission near 100%, realizing a near perfect tunable THz filter or modulator.
Monday, June 22, 2015
Abstract-Hybrid Metal-Graphene Plasmons for Tunable Terahertz Optoelectronics
(Submitted on 18 Jun 2015)