We report a normal-incidence grating coupler that is monolithically integrated with a GexSi1−x rib waveguide. The design, fabrication, and testing procedures are described for a 0.33-μm-period grating coupler integrated with a Ge0.04Si0.96 waveguide. Also, a theoretical analysis based on coupler-mode theory has been carried out to predict the coupling efficiency and its dependence on the angle of incidence of light. For normal incidence the measured efficiency of 6.5% was found to be in good agreement with the theoretical prediction of 6.9%. The measured FWHM of the acceptance angle about the normal was 5°, compared with the theoretical prediction of 3°.
© 1994 Optical Society of America
Original Manuscript: February 1, 1994
Published: June 1, 1994
J. Sarathy, R. A. Mayer, K. Jung, S. Unnikrishnan, D.-L. Kwong, and J. C. Campbell, "Normal-incidence grating couplers in Ge-Si," Opt. Lett. 19, 798-800 (1994)