Reflectance of an absorbing substrate for incident light of arbitrary polarization: appearance of a secondary maximum at oblique incidence

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Abstract
The reflectance of an absorbing substrate Rθ(ϕ) is considered as a function of the angle of incidence ϕ and an incident polarization parameter θ, where cos2θ and sin2θ give the power fractions of incident radiation that are p-and s-polarized, respectively. Taking GaAs as an example, we find that at certain wavelengths (e.g., 0.248 and 0.620 μm), the Rθ vs ϕ curve becomes oscillatory in a narrow range of θ > 45° with an unexpected secondary maximum appearing at oblique incidence. The extrema of the function Rθ(ϕ) are determined numerically, and their angular positions and reflectance levels are plotted vs θ for GaAs at photon energies of 1, 2, and 5 eV.