Graphene Integrated in a Ring Type Fabry-Perot Cavity: Polarization Insensitive, Low Voltage and Tunable Modulation of Light at Near-IR Telecommunications Band

In this article, a novel graphene based resonant free space modulator for modulating optical signals in the wavelength range of 1-2 μm is designed and numerically investigated. The presented modulator is highly versatile. It can function in both transmission and reflection regimes and is polarization insensitive and can be easily tuned to any particular wavelength. In this device, an ingenious Fabry-Perot (FP) cavity composed of concentric Au disks and rings and a single layer graphene is proposed. Incoming light is totally transmitted provided that the wavelength coincides the resonant wavelengths of the cavity, otherwise it is reflected. Hence, unlike common graphene modulators based on electro-absorption, here, the main role of graphene is to shift the resonant wavelengths of the FP cavity and its absorption is indeed negligible. Several highly efficient modulators are designed which can be summarized as follows: A transmission (reflection) type modulator with central wavelength of 1.55 μm, modulation depth of 95% (92%) at this wavelength, modulation depth of 48% (46%) in the wavelength range of 1.42- 1.63 μm (1.46-1.6 μm) covering entire C+S bands, insertion loss of 1.5 dB (1.3 dB) and gate voltage of 4.5 V (4.2 V). Other narrow band low voltage modulators requiring voltages of less than 1.5 V are designed either.