Compact InGaAsP/InP Asymmetric Mach–Zehnder Coupled Square Ring Modulator

We propose a compact InGaAsP/InP electro-optic ring modulator operated with coupling modulation that can circumvent the bandwidth limitation and large minimum bend radius of a ring. This device consists of frustrated total internal reflection (TIR) couplers and TIR mirrors serving as 90° waveguide bends, forming the configuration of an asymmetric rectangular Mach-Zehnder interferometer coupled to a square ring resonator (SRR). A discrete-time dynamic model and finite difference time-domain method are used to evaluate the device performances, and the theoretical results show an operating frequency up to 60 GHz, the maximum extinction ratio of ~12 dB, the low electrical energy of ~60 fJ/bit, and a compact chip size of ~18 μm x 29 μm, respectively. The enabling component of the SRR represents >100-fold footprint reduction on a chip. This compact device can be potentially applied in large-scale InP-based photonic integrated circuits.