Refractive Index: A Complex Number

doi:10.1117/3.2506314.ch3

Book: Wave Optics: Lectures in Optics, Volume 3

Author(s): George Asimellis

Published: 2020

https://doi.org/10.1117/3.2506314.ch3

Abstract

Geometrical optics accepts certain convenient simplifications. One of these approaches is to treat the refractive index as a fixed, real number. This simplification is adopted despite strong indications that the refractive index is wavelength dependent. What more would we need than the analysis of colors through a prism or the chromatic aberrations in lenses? In addition, birefringence indicates that the refractive index in optical anisotropic materials is not just a number, but a 3×3 tensor; in other words, it is not one, but nine numbers, which, in principle, means that the numbers are complex! However, this simplification is quite a useful approach.