Quasi index matching for minimum reflectance at a dielectric-conductor interface for obliquely incident p- and s-polarized light

摘要

Conditions for reducing the reflectance of a dielectric-conductor interface for p- and s-polarized light to a minimum at any angle of incidence phi are determined. The refractive indices of a transparent immersion medium (liquid) that achieve minimum reflectance at normal incidence, phi velence 0, and at phi velence 45 deg are independent of polarization. These indices provide sufficient data to determine the real and imaginary parts of the complex refractive index of an absorbing substrate. Reflection at a dielectric-Au interface at 500 nm wavelength is considered as an example. It is shown that the lowest possible reflectance is attained for p-polarized light at phi velence 45 deg and that the associated p-reflection phase shift is also minimum at that angle. For phi >= 65 deg the lowest reflectance of p-polarized light occurs when the ambient is vacuum or air. However, this lowest reflectance at the air-Au interface is not a true minimum in a mathematical sense.