Optimization and Demonstration of a Large-bandwidth Carrier-depletion Silicon Optical Modulator

Abstract

We present the design, fabrication, and measurement of a high-speed carrier-depletion silicon optical modulator based on Mach-Zehnder Interferometer structure. Based on an equivalent circuit model, the traveling-wave electrode size and doping concentration of the PN junction are optimized to achieve a large modulation bandwidth. The modulation efficiency and optical loss at different positions of the PN junction are also simulated. The device is fabricated on silicon-on-insulator (SOI) with 0.13 μm CMOS technology. An insertion loss of 3.9 dB (resp. 6.2 dB) and a VπLπ of 1.62-2.05 V·cm (resp. 1.47-1.97 V·cm) are experimentally realized for 1 mm (resp. 2 mm) long phase shifter. By small signal measurement, the modulator exhibits a 3 dB bandwidth of 30 GHz and 19 GHz for 1 mm and 2 mm long phase shifter, respectively, which agrees well with the simulation results. The optical eye diagram with data rate up to 44 Gb/s is also demonstrated, showing potential in the application of high-speed optical interconnects.