Patent ID: 7676128
Filing Date: 2010-03-09
Classification: G02B

Abstract:
1. An optical apparatus comprising a set of diffractive elements on a substrate that are arranged: (i) to receive at least a portion of an input optical signal propagating from an input optical port as a diffraction-guided optical beam, (ii) to diffract a portion of the received input optical signal as an output optical signal, and (iii) to route the output optical signal to propagate to an output optical port as a diffraction-guided optical beam, wherein: each diffractive element comprises at least one trench between ribs projecting from the substrate surface; at least one side surface of each trench is substantially perpendicular to the bottom surface of that trench, so that the diffractive element set formed on the substrate exhibits relatively enhanced diffraction efficiency near a Littrow arrangement of the input and output optical ports relative to the substrate; and the depth of at least one trench is equal to about half of its width divided by the tangent of a selected Littrow angle of incidence.