Design of integrated optoelectronic switch

Abstract

Processing data at optical wavelengths has a number of advantages, particularly in terms of bandwidth and light is believed to be one of the most promising possibilities for replacing electronic signals as information carriers. Photonic devices are quickly gaining importance as potential saviors for meeting bandwidth demands in communication networks and high-speed computing. Silicon photonics offers a viable foundation for constructing highly scalable, low-cost on chip photonic devices. However, Si photonics has a poor electro refractive effect associated with a larger footprint, losses, and high energy consumption. As a solution, Si photonics is looking for a low cost active material that can be used in conjunction with Si to achieve critical performance parameters. Graphene has unique electrical and optical properties, making it a good candidate for use as an active material in silicon photonics to improve light modulation, switching, and detection. Ring resonators serve a key role in lowering the size of Si photonics. In this thesis, a nanophotonic switch based on an electrically tunable graphene-silicon ring resonator is proposed and optical switching is realized by tuning the resonant wavelengths of the ring resonator. The shift in resonant wavelengths of the ring is achieved through modulation of the Fermi energy level of graphene by means of electrical gating. The hybrid plasmonic structure of the ring confines the light in nanoscale dimensions. The gap and length of the ring are optimized for a better extinction ratio. At a wavelength of 1550 nm, the proposed optical switch has an extinction ratio of 10.94 dB. A minimum gap of 100 nm and a smaller ring radius of 3.1 μm offers a minimal footprint area. The real and imaginary parts of the effective index of the ring w.r.t voltage across the graphene are observed. The results pave the path for more optical switches, and modulators based on electrically controllable characteristics of the graphene and the ring resonator. The proposed design finds applications in optical interconnects, optical SRAM’s and other integrated photonic devices.