High-index dielectric substrates with nearly constant reflectance for incident unpolarized or circularly polarized light over a wide range of incidence angles

Abstract

Dielectric substrates with refractive indices in the range n1 ≤ n ≤ n2, and exhibit nearly constant reflectance for incident unpolarized or circularly polarized light Ru(ϕ) over a wide range of incidence angle ϕ. For , Ru(ϕ) increases monotonically from at normal incidence by only 0.06% at ϕ = 45° and 1% at ϕ = 60°. For n2 = 4.6116, at the Brewster angle ϕB = 77.77° and the normalized reflectance shift |(Ru − R0)/R0| is < over the extended range 0 ≤ ϕ ≤ 80°. Apart from a small imaginary part (k << n), refractive indices of semiconductor substrates (e.g. Ge and GaAs) fall in the range n1 ≤ n ≤ n2 and hence exhibit nearly constant reflectance for incident unpolarized light over a wide range of incidence angles at IR and visible wavelengths.