Patent ID: 7687760

Claim:
An optical coupling structure intended to couple electromagnetic radiation to the surface of a photodetector, comprising: an ohmic contact layer having an optical coupling surface comprising a set of N series of first, second, . . . nth identical elementary cells within the same series, each first, second, . . . nth elementary cell, wherein for each type cell, a raised feature is formed at the center of the cell and extends outward therefrom, and an etched distance between each said feature is variable within the structure, and wherein the ohmic contact layer has a thickness of about 2 microns and an etch depth of about 1.2 microns; wherein the features comprise first features, second features, . . . nth features, the features being identical within any one series, the features being distributed along mutually perpendicular first and second directions, the etched distance between the centers of two adjacent features or the inter-reticular distance etched between two adjacent features being variable and the first, second, . . . nth features being of square shape and/or of rectangular shape; wherein said features in said first direction are responsive to multiple wavelengths such that the periodic effects in said photodetector are eliminated while the range of detectable wavelengths is expanded to a broader spectral band; and wherein said features in said second direction are responsive to multiple wavelengths such that the periodic effects in said photodetector are eliminated while the range of detectable wavelengths is expanded to a broader spectral band.