Analysis of Silicon Racetrack Modulator Employing Coupling Modulation via Active MMI Coupler

Abstract

In this paper, we propose and analyze the performance of a high-speed racetrack resonator (RTR)-based intensity modulator, which uses coupling coefficient modulation. The proposed modulator is realizable on the standard 220-nm silicon-on-insulator platform. The intensity modulation is achieved by modulating the coupling coefficient between the RTR and the access waveguide using a lateral p-i-n-diode-based active multimode interference (MMI) coupler. The coupling coefficient modulation has been achieved by creating a small perturbation in the refractive index profile inside the active MMI coupler. Theoretical analysis of the proposed modulator using the first-order perturbation theory and time-dependent dynamic model is presented. Analysis and simulation showed that the proposed modulator offers minimum 15.1 dB of static extinction ratio (ER) and ~5.4 dB of dynamic ER at 32 Gb/s data rate. It has been shown that the modulator can be designed for both 0.8 and 1.6 nm free spectral range and the required driving voltage is ~1.3 V. Both transient analysis and the small-signal model of the proposed modulator verify the maximum operating speed up to 32 Gb/s. Also, our analysis predicts that the power dissipation for the proposed modulator at 32 Gb/s is approximately 2.97 mW and thus, the energy dissipation per bit is ~86 fJ.