Reflection Difference Techniques

Reflectance measurements are conventionally used to derive the optical constants of solid materials, i.e. the refractive index, N, and the extinction coefficient, K. At near normal incidence, for example, the reflectance, R, (the ratio of the reflected to incident EM intensity: see Sect. 1.3) is given by: (4.1)$$R = \frac{{{{(n - 1)}^2} + {\kappa ^2}}}{{{{(n + 1)}^2} + {\kappa ^2}}}$$ The optical constants are related to the dielectric function, ε = ε’ + iε” by: (4.2)$$\varepsilon ' = {n^2} - {\kappa ^2}{\text{ and }}\varepsilon '' = 2n\kappa $$