Silicon Photonic Devices based on Segmented Waveguides

Abstract

Silicon holds a great potential as the material for implementing photonic devices because of the possibility to leverage mature CMOS fabrication technologies developed for microelectronic industry, enabling cost-effective volume production. In this thesis, three silicon photonic devices are developed, a wideband and compact TM-pass polarizer, a silicon microring resonator modulator compatible to zero-change foundry CMOS process, and a highly sensitive, fully suspended microring resonator sensor. First, a Transverse-Magnetic (TM) polarizer using segmented waveguides is proposed, which scatters the Transverse-Electric (TE) mode and passes through TM mode. The simulated 27.4μmlong device has insertion loss and extinction ratio of less than 0.1dB and more than 30dB, respectively. The polarizer was fabricated on a silicon chip and characterized experimentally. The 144μm-long device had insertion loss of 1.4-2.3dB and extinction ratio of 18-29dB, likely limited by experimental setup, over 110nm of optical bandwidth. Second, a ring resonator modulator using segmented waveguides is proposed with the goal of eliminating the need for partial silicon etch when making electrical contacts, which makes the modulator compatible to zero-change foundry CMOS processes. The undoped structure is predicted to have an intrinsic quality-factor of 50k and free-spectral-range of 13.4nm for a 10μm ring radius. Doping the resonator to create a p-n junction reduces the Q-factor to 16k and allows to achieve modulation efficiency of 1.4V•cm at 0.8V reverse bias. The peak-to-peak voltage required for 10dB extinction ratio is 1.6V, and the insertion loss is 2dB, as predicted by rigorous optical and semiconductor device simulations. Finally, a fully suspended microring resonator sensor based on a segmented waveguide is proposed. Simulations predict very high sensitivity of 500-800nm/RIU in an optimized resonator structure.

Date of Award	May 2015
Original language	American English
Supervisor	Anatol Khilo (Supervisor)