Multilayer anti-reflection coating - for low refractive index substrates, effective in visible to near-IR range

摘要

A multilayer coating, for reducing reflection of low refractive index substrates in the visible and near-IR range, consists of a high refractive index layer-forming substance (H) with a refractive index of at least 2.0 and of a low refractive index layer-forming substance (L) with a refractive index of max. 1.6, the substances being applied as alternate layers on the substrate. The novelty is that the coating comprises, between a substrate with n (refractive index) = at least 1.45 and air with n = 1.0003, the following layers: (i) a first H layer with d (geometrical layer thickness in nm) = 11.5-17.5; (ii) an L layer with d = 43.5-55.5; (iii) an H layer with d = 33.0-45.0; (iv) an L layer with d = 15.0-22.0; (v) an H layer with d = 110.0-144.5; (vi) an L layer with d = 17.0-24.5; (vii) an H layer with d = 26.5-34.5; and (viii) a final L layer with d = 111.0-126.0. USE/ADVANTAGE - The coating is esp. useful for optical transmission elements of glass, plastics or crystal. It ensures a residual reflection of less than 0.9% over the 450-1100 nm spectral range including the laser wavelength of 1.06 microns, employs only two layer materials and can be produced at low cost by conventional vapour deposition.