title: Compact double-grating coupler between vertically stacked silicon-on-insulator waveguides.
abstract: We analyze a compact double-grating coupler that provides coupling through radiation modes between two vertically stacked silicon-on-insulator waveguides. The grating is sufficiently strong to be considered a one-dimensional photonic bandgap structure that facilitates a short coupling length. Simulations suggest that a 29% coupling efficiency is achievable in coupling light from one waveguide to another with 12.9 microm long binary gratings. We found that the coupling efficiency is enhanced by Fabry-Perot resonance between two gratings. The coupling efficiency can be increased by use of a blazed grating. We use the eigenmode expansion method to design and optimize the binary grating coupler, and the results are verified by use of the finite-difference time-domain method.
authors.affiliation: Photonic Systems Group, Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, Quebec H3A 2A7, Canada. podong@photonics.ece.mcgill.ca
authors.forename: Po
authors.initials: P
authors.lastname: Dong
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Kirk