Polarization Insensitive Silicon Photonics Fiber to Chip Coupler

Abstract

Silicon photonics allows us to fabricate high density photonic integrated circuits (PICs) because of the high refractive index contrast and compatibility with the complementary metal-oxide-semiconductor (CMOS) process. Most silicon photonics components are designed for only single polarization operation. However, the state of polarization (SOP) of light in a fiber is unpredictable. For this reason, a polarization insensitive fiber to chip coupler is needed. In this thesis, we designed and fabricated a polarization insensitive silicon photonics fiber to chip coupler. We can couple the light with an arbitrary SOP from the fiber to the TE mode of a silicon waveguide. A 2D grating coupler, phase shifter, and 3 dB coupler are used to make the device. In detail, we designed a 2D grating coupler for polarization insensitive fiber to chip coupling. Further, we used a microelectromechanical system (MEMS) phase shifter and adiabatic 3 dB coupler to combine the lights that are divided after the 2D grating coupler. Using these components, we can expect a relatively broadband operation and low power consumption compared with previously reported devices. The fabricated 2D grating coupler shows a maximum transmission of -6.72 dB at 1532 nm and a 1 dB bandwidth of 38 nm with s-polarization. With p-polarization, the maximum transmission is -7.91 dB at 1245nm, and 1 dB bandwidth is 35 nm. Polarization dependent loss (PDL) is less than 2 dB in the bandwidth range.