Proposal and Simulation of a Compact SIS-type MZ Modulator with CROW Structure for Optical I/O Applications

We propose a semiconductor-insulator-semiconductor (SIS)-type Mach-Zehnder modulator (MZM) featuring a Bragg grating-based coupled-resonator optical waveguide (CROW) structure in the optical phase shifters (OPSs). The CROW structure and the SIS-type OPS offer the benefits of a significantly higher group index and modulation efficiency, respectively, enabling a remarkably short optical phase shifter of 130 µm. We have investigated and optimized the CROW structure to achieve a group index ranging from 12 to 16 and an optical passband of 4 to 5 nm. Additionally, we numerically simulated the MZM's performance using TCAD simulation, which reveals a transmitter penalty of 6 dB at 40 GHz and 8 dB at 50 GHz. This would be a promising solution for optical input/output (I/O) applications.