Canonical Models of Dielectric Response

The interaction of electromagnetic fields with a solid is characterized by several interconnected response functions: the dielectric function $\varepsilon(\omega)$, index of refraction $N(\omega)$, conductivity $\sigma(\omega)$, and optical impedance $Z(\omega)$. Here we utilize three canonical models of dielectric response -- the damped harmonic oscillator, Debye polarization response, and the Drude model -- to discuss these four optical response functions. Special emphasis is devoted to the response of a Drude metal. Our main focus is on electromagnetic wave propagation through a material. We also discuss the relaxation of charge fluctuations within the context of the three canonical models of response.