Patent ID: 8989537
Filing Date: 2015-03-24
Classification: B29D,G02B

Abstract:
1. An optical transmission grating positioned within an ambient medium, the ambient medium being substantially transparent over an operational wavelength range and characterized by an ambient medium refractive index n A , the optical transmission grating comprising: (a) a substrate comprising a non-gaseous material that is characterized by a substrate refractive index n (b) a first impedance matching layer of thickness t (c) a set of multiple, discrete, spaced-apart, elongated ridges of thickness t (d) a second impedance matching layer covering the ridges to a thickness t wherein: (e) for at least a first localized area of the grating, the set of ridges is characterized by a first grating spacing Λ, a first ridge width w<Λ, and a first grating wavevector direction; (f) a bottom surface of the second dielectric material of each ridge is in contact with the first dielectric material of the first impedance matching layer, and top and side surfaces of the second dielectric material of each ridge are in contact with the third dielectric material of the second impedance matching layer; (g) over at least the operational wavelength range, (i) n (h) for at least one selected incidence angle θ (i) the set of ridges and the first and second impedance matching layers are structurally arranged in the first localized area of the grating so that n