GRATING COUPLER ACCEPTANCE DESIGN UTILIZING A TAPERED WAVE-GUIDE STRUCTURE

A tapered waveguide film was deposited on a substrate with a grating s tructure resulting in a hybrid thin-film waveguide coupler that could be designed for a broader or narrower acceptance for wavelength or inc idence angle. The optimized couplers were designed and fabricated. The couplers were found to be as efficient as traditional grating coupler s but with much broader acceptance. The maximum broadening was calcula ted to be a coupling FWHM of 2-degrees (or 12 nm) and was confirmed ex perimentally. This is 4.3 times the acceptance of an identical untaper ed structure.