Ultra-fast tunable optoelectronic full-adder based on photonic crystal ring resonators covered by graphene nanoshells

Abstract

This paper reports a novel design of a tunable optoelectronic full-adder using two photonic crystal ring resonators (PCRRs). Every PCRR consists of a matrix of silicon rods surrounded by silica rods coated with graphene nanoshells (GNSs). The proposed full-adder is formed by three input ports, two PCRRs, and two output ports for ‘SUM’ and ‘CARRY’. The plane wave expansion technique is used to study the photonic band structure of the fundamental photonic crystal (PhC) microstructure, and the finite-difference time-domain method is also employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We can tune the PhC resonant mode for our desired application by setting the chemical potential of GNSs with an appropriate gate voltage. The numerical results reveal that when the chemical potential of GNSs changes, the switching mechanism occurs and manages the coupling and propagation direction of the input beam inside the structure. We systematically study the effects of physical parameters on the transmission, reflection, and absorption spectra . Our numerical results also demonstrate that the maximum delay is about 0.8 ps. The 663 μm 2 area of the proposed full-adder based on two-dimensional materials makes it a building block of every photonic integrated circuit used for data processing systems. • A fast and compact all-optical full-adder using photonic crystal ring resonators (PCRRs). • A maximum steady-state time of about 0.8 ps and the structure's total size of 663 μm 2 . • There is no need to increase the input intensity for the appearance of the nonlinear effect. • The ON-OFF contrast ratios for Sum and Carry are 16 dB and 14 dB, respectively. • The full-adder is applicable in optical integrated circuits for high-speed signal processing.