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 µm 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.
© 2005 Optical Society of America
Original Manuscript: October 28, 2004
Revised Manuscript: January 11, 2005
Manuscript Accepted: August 18, 2005
Published: December 10, 2005
Po Dong and Andrew G. Kirk, "Compact double-grating coupler between vertically stacked silicon-on-insulator waveguides," Appl. Opt. 44, 7540-7547 (2005)