Optical device including waveguide grating structure

A method, comprising:

• causing an optical apparatus to be positioned in the path of incident electromagnetic radiation, the optical apparatus comprising a horizontal waveguide grating structure (WGS) having at least one waveguiding layer and at least one subwavelength periodic grating layer, the optical apparatus further having upper and lower cladding layers immediately adjoining respective upper and lower surfaces of the WGS and having refractive indices lower than a lowest-index one of the waveguiding layers, wherein the incident radiation propagates in a generally downward direction toward the WGS through the upper cladding layer;
• and
• receiving one of radiation reflected upwardly from the WGS through the upper cladding layer and radiation propagated downwardly through the WGS and the lower cladding layer;
• wherein the WGS is configured for peak upward reflection of the incident radiation at a peak reflection frequency;
• and
• wherein a cumulative thickness of the waveguiding layers is less than one tenth of a free space wavelength of the incident radiation at the peak reflection frequency divided by an average refractive index of the waveguiding layers.

An apparatus, comprising:

• a optical source providing a source beam;
• a horizontal waveguide grating structure comprising at least one waveguiding layer and at least one subwavelength periodic grating layer, said waveguide grating structure having upper and lower surfaces defined by an uppermost one and a lowermost one of said waveguiding and subwavelength periodic grating layers, respectively, said waveguide grating structure being disposed beneath said optical source;
• upper and lower cladding layers extending upward from said upper surface and downward from said lower surface, respectively, said upper and lower cladding layers having refractive indices lower than a lowest-index one of said waveguiding layers, said upper cladding layer being disposed beneath said optical source;
• an optical receiver positioned to receive one of radiation reflected upwardly from the WGS through the upper cladding layer and radiation propagated downwardly through the WGS and the lower cladding layer;
• wherein said WGS is configured for peak reflection of said source beam at a peak reflection frequency;
• and
• wherein a cumulative thickness of said waveguiding layers is less than one tenth of a free space wavelength of the source beam at said peak reflection frequency divided by an average refractive index of said waveguiding layers.