Surdutovich G, Vitlina R, Baranauskas V
Departamento de Semicondutores, Instrumentos e Fotônica, Faculdade de Engenharia Elétrica e de Computacão, Unicamp, CEP 13083-970 Campinas, São Paulo, Brazil.
Appl Opt. 1999 Jul 1;38(19):4164-71. doi: 10.1364/ao.38.004164.
A method for determining the optical properties of a film on an isotropic substrate is proposed. The method is based on the existence of two specific incidence angles in the angular interference pattern of the p-polarized light where oscillations of the reflection coefficient cease. The first of these angles, theta(B1), is the well-known Abelès angle, i.e., the ambient-film Brewster angle, and the second angle theta(B2) is the film-substrate Brewster angle. In the conventional planar geometry and in a vacuum ambient there is a rigorous constraint epsilon(1) + epsilon > epsilon(1)epsilon on the film and the substrate dielectric permittivities epsilon(1) and epsilon, respectively, for the existence of the second angle theta(B2.) The limitation may be removed in an experiment by use of a cylindrical lens as an ambient with epsilon(0) > 1, so that both angles become observable. This, contrary to general belief, allows one to adopt the conventional Abelès method not only for films with epsilon(1) close to the substrate's value epsilon but also for any value of epsilon(1). The method, when applied to a wedge-shaped film or to any film of unknown variable thickness, permits one to determine (i) the refractive index of a film on an unknown substrate, (ii) the vertical and the horizontal optical anisotropies of a film on an isotropic substrate, (iii) the weak absorption of a moderately thick film on a transparent or an absorbing isotropic substrate.
提出了一种测定各向同性衬底上薄膜光学特性的方法。该方法基于在p偏振光的角干涉图样中存在两个特定入射角，此时反射系数的振荡停止。其中第一个角度θ(B1)是著名的阿贝莱斯角，即环境-薄膜布儒斯特角，第二个角度θ(B2)是薄膜-衬底布儒斯特角。在传统的平面几何结构和真空环境中，对于第二个角度θ(B2)的存在，薄膜和衬底的介电常数ε(1)和ε分别存在严格的约束条件ε(1)+ε>ε(1)ε。在实验中，可以通过使用介电常数ε(0)>1的柱面透镜作为环境来消除该限制，这样两个角度都可以观测到。与普遍看法相反，这使得不仅可以将传统的阿贝莱斯方法用于ε(1)接近衬底值ε的薄膜，还可以用于任何ε(1)值的薄膜。该方法应用于楔形薄膜或任何厚度未知的可变薄膜时，可以确定：(i)未知衬底上薄膜的折射率；(ii)各向同性衬底上薄膜的垂直和水平光学各向异性；(iii)透明或吸收性各向同性衬底上中等厚度薄膜的微弱吸收。
