Optical Properties of Thin Absorbing Films*

Abstract

Equations are given for the reflectances, transmittances, and phase changes by reflection and transmission of very thin absorbing films, i.e., films with a thickness d very small compared with the wavelength λ of the incident radiation. The similarities and differences between very thin homogeneous and inhomogeneous films are discussed, and some experimental results obtained on very thin gold and chromium films are presented. We measured the reflectance and transmittance of these films as a function of the angle of incidence φ₀ and of the state of polarization of the incident light. A new method is given for obtaining the optical constants of ionic crystals in the infrared. The optical properties of thick metallic films, with some new photometric methods for the determination of their optical constants, are discussed. The theory of the optical absorption of metals is briefly presented.