Grating coupler acceptance design utilizing a tapered waveguide structure.

A tapered waveguide film was deposited on a substrate with a grating structure resulting in a hybridthin-film waveguide coupler that could be designed for a broader or narrower acceptance for wavelength or incidence angle. The optimized couplers were designed and fabricated. The couplers were found to be as efficient as traditional grating couplers but with much broader acceptance. The maximum broadening was calculated to be a coupling FWHM of 2° (or 12 nm) and was confirmed experimentally. This is 4.3 times the acceptance of an identical untapered structure.