Raik Elster

Abstract

A compact integrated and high-efficiency polarization mode interferometer in the 220-nm silicon-on-insulator platform is presented. Due to the operation with two polarization modes in a single waveguide, low propagation losses and high sensitivities combined with a small footprint are achieved. The designed and fabricated system with a 5-mm-long sensing region shows a measured excess loss of only 1.5 dB with an extinction ratio up to 30 dB, while its simulated homogeneous bulk sensitivity can exceed 8000 rad/RIU. The combination with a 90°-hybrid readout system offers single wavelength operation with unambiguousness for phase shifts up to 2pi and constant sensitivity.

Abstract

In photonic integrated circuits grating couplers are commonly used to establish an efficient and stable fiber-to-chip link. However, the actual coupling efficiency of a fiber-to-chip interface depends strongly on the used wavelength and exhibits a maximum at a distinct target wavelength, determined by grating design parameters. In this paper, an enhancement of the optical bandwidth of silicon grating couplers by adding integrated dispersive structures is discussed. These are realized by single layers, prism-like geometries and additional SiN gratings. Theoretical considerations for a bandwidth-enhancement by dispersive layers are performed and applied to an existing grating coupler design. A simulated 1dB-bandwidth of up to 90 nm at a maximum efficiency of -0.65 dB in the C-band could be achieved, which is an enhancement to a factor of about 2 compared with the original coupler design.