Patent ID: 7184627

Claim:
A waveguide grating coupler for coupling light between a waveguide and an optical element having a substantially Gaussian mode profile, said waveguide grating coupler comprising: a planar guiding portion optically connected to said waveguide, said planar guiding portion having first and second ends and an optical power distribution therein that decreases between said first and second ends; and a plurality of elongate scattering elements having respective scatter cross-sections arranged along at least a portion of said planar guiding portion to couple light having a substantially Gaussian intensity distribution between said planar guiding portion and said optical element, said elongate scattering elements having at least one characteristic which varies in magnitude among at least a group of said elongate scattering elements, said magnitude of said characteristic controlling at least in part said scatter cross-sections of said elongate scattering elements, wherein said magnitude of said characteristic of said group of elongate scattering elements varies irregularly, said magnitude for said group of elongate scattering elements changing with position along said planar guiding portion at a rate that is discontinuous, wherein (i) said plurality of elongate scattering elements have respective scatter cross-sections adapted to scatter light along at least a portion of a predetermined optical path and (ii) said planar guiding portion further comprises a Distributed Bragg Reflector (DBR) positioned with respect to said elongate scattering elements such that light scattered outside said portion of said optical path is reflected by said DBR towards said elongate scattering elements.