Fundamental optical properties of materials

Optical properties of a material change or affect the characteristics of light passing through it by modifying its propagation vector or intensity. Two of the most important optical parameters are the refractive index and the extinction coefficient, which are generically called optical constants, although some authors include other optical coefficients within this terminology. This chapter presents the refractive index and extinction coefficient in detail, along with some common dispersion relations. It presents various common dispersion relationships such as the Cauchy, Sellmeier, Wemple-DiDomenico dispersion relations, and explains the determination of the optical constants of a material in thin film form using the popular Swanepoel technique. The latter technique is based on the interference of waves in the thin film, and uses the maxima and minima in the transmittance spectrum to extract the dispersion relation for refractive index and extinction coefficient. The chapter also considers the transmittance of light through a thick semitransparent plate.