High Bandwidth Capacitance Efficient Silicon MOS Modulator

This article analysed and optimised horizontal Silicon insulator Silicon capacitor (H-SISCAP) phase shifter structures with insulator thickness t _ox up to 40 nm. The phase shifter has an effective capacitance (Ceff) around 0.5 fF/μm and a phase change efficiency 1.8 V·cm, of which the balance between capacitance and phase efficiency is comparable with silicon rib waveguide based depletion type phase shifters. Silicon Mach-Zehnder interferometer (MZI) modulators with 200 μm long H-SISCAP phase shifters optimised for TM polarised light have been fabricated and demonstrated with a 3 dB EO bandwidth above 35 GHz and intrinsic H-SISCAP RC bandwidth around 150 GHz. The modulator displays open eye-diagrams for data rates up to 60 Gbit/s without detection equalization and 72 Gbit/s with 2 taps equalization in NRZ-OOK operation. The demonstrated H-SISCAP phase shifter paves the way to build high bandwidth segmented, travelling wave and compact ring resonators modulators for applications of optical transmitters, microwave generations, and LIDAR applications, etc.