First numerical examples
Optical thin films and interferential filtering

In what follows, we will consider dielectric materials, i.e. those with low dissipation (low absorption): the imaginary part of the refractive index is smaller than the real part. A high or low index material is a quasi-transparent material whose real refractive index (n_H or n_B) is higher (n_H > n_s) or lower (n_B < n_s) than the substrate's real index n_s. The dielectrics used for the numerical calculation are generally air (superstrate index n₀ = 1), glass (substrate index n_s = 1.52), zinc sulfide (ZnS) index n_H = 2.3 and cryolite (Na₃AlF₆) index n_B = 1.3, although the latter two materials are now rarely used. These index values are given for wavelength λ = 633 nm. Index dispersion is neglected for simplicity. We also restrict ourselves to the visible spectrum....