Patent ID: 7572512

Claim:
An infrared transmissive article, comprising: an infrared (IR) transmissive substrate, and a single layer anti-reflective (AR) sol-gel composite broadband coating on a surface of said substrate, said single layer AR coating comprising: a first metal or semiconductor chalcogenide comprising compound, said first metal or semiconductor chalcogenide compound being essentially all in a metal or semiconductor chalcogenide form; a second chalcogenide comprising compound different from said first chalcogenide comprising compound intermixed with said first chalcogenide comprising compound, said second metal or semiconductor chalcogenide compound being essentially all in a metal or semiconductor chalcogenide form; wherein percentages of said first chalcogenide and said second chalcogenide in said single layer AR coating are selected provide a refractive index of said single layer AR coating that approximates the square root of a refractive index of said substrate, and wherein said AR coating is in a highly amorphous state.