Patent ID: 9323070
Filing Date: 2016-04-26
CPC Classification: G01J,G02B,H01S

Claim Text:
1. Method of manufacturing a master grating for diffracting light of a particular wavelength impinging the master grating with a particular angle of incidence, the master grating comprising an array of grooves running in parallel along a planar face of the master grating, the grooves distanced by a grating period; the grooves comprising a triangular profile with flat interfaces, wherein one of the interfaces forms a blaze angle with respect to the planar face; wherein the method comprises providing a wafer comprising a substantially mono-crystalline material, the material having first, second, and third crystal planes, wherein the first and second crystal planes intersect each other at an intersection angle; the wafer being cut along a wafer surface having a cut angle equal to the blaze angle with respect to the first crystal plane; applying an etching resistant material to parts of the wafer surface in a pattern of parallel strips, the centers of the strips distanced by the grating period, wherein exposed parts of the wafer surface are formed between the strips; applying an anisotropic etching process to the wafer surface that etches faster in a direction normal to the third crystal plane than in a direction normal to the first and second crystals planes to form the grooves at the exposed parts wherein the flat interfaces of the grooves are formed along the first and second crystal planes; wherein the method further comprises calculating a corrugation amplitude of the grooves with respect to the wafer surface as a function of a desired diffraction efficiency of the light for the given grating period and blaze angle; and in the applying of the etching resistant material, controlling a line width of the strips such that the grooves are formed with the flat interfaces extending from exposed edges of neighboring strips into the wafer surface and intersecting each other with the intersection angle at a depth equal to the calculated corrugation amplitude.