Design and Simulation of Compact Optical Modulators and Switches Based on Si–VO2 –Si Horizontal Slot Waveguides

Abstract

In this paper, a horizontal slot Si-VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -Si optical waveguide is proposed and its optical properties are investigated. Numerical simulation results show that the effective index and the propagation loss of the proposed waveguide undergo substantial changes upon the VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> transition from insulating to metallic phase. The effective index and the propagation loss variations of the proposed waveguide are then maximized by optimizing waveguide dimensions. It is shown that 0.226 change in the effective index (Δn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> = 0.226) and 30 dB/μm change in the propagation loss (Δl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dB</sub> = 30 dB/μm) are achievable using the optimum dimensions. These extraordinary variations in waveguide properties recommend the proposed waveguide as an excellent candidate for optical active device realization. To investigate these applications, performance parameters of the proposed waveguide are further studied in terms of the transition speed and the power consumption. In these studies, the VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> phase transition is assumed to be actuated by applying an electric field. Two examples of optical active devices based on the proposed waveguide are then presented: an electro-absorption modulator and a 1 × 2 directional coupler optical switch. Finite-difference time-domain simulation of the proposed devices shows very high extinction ratio of 21 dB along the ultrasmall propagation length of 1 μm, for the proposed electro-absorption modulator, and high extinction ratios of ~18.5 dB and ~8.6 dB in off- and on-state of the proposed 1 × 2 switch, which has very small length of ~6 μm. Further simulations also show interesting properties of the proposed devices in terms of the power consumption, insertion loss, and bandwidth.