Cauchy model Refractive index wavelength dependence is specified: $$n(\lambda)=A_0+\displaystyle\frac{A_1}{\lambda^2}+\frac{A_2}{\lambda^4}$$ Sellmeier model In OptiLayer, Sellemeier model is represented in different forms. Refractive index wavelength dependence is specified: $$n^2(\lambda)=A_0+\displaystyle\frac{A_1\lambda^2}{\lambda^2-A_2}$$ $$n^2(\lambda)=A_0+\displaystyle\frac{A_1\lambda^2}{\lambda^2-A_2}+\frac{A_3\lambda^2}{\lambda^2-A_4}$$ $$n^2(\lambda)=A_0+\displaystyle\frac{A_1\lambda^2}{\lambda^2-A_2}+A_3\lambda^2$$ $$n^2(\lambda)=A_0+\displaystyle\frac{A_1\lambda^2}{\lambda^2-A_2}+\frac{A_3\lambda^2}{\lambda^2-A_4}++\frac{A_5\lambda^2}{\lambda^2-A_6}$$ Arbitrary dispersion Arbitrary dispersion model assumes Cauchy model for the refractive index. The coefficients of the Cauchy model vary in arbitrary way in the course of the characterization process. Exponential model for extinction coefficient Dispersion behavior of extinction coefficient is described by exponential formula: $$k(\lambda)=B_1\exp\{B_2\lambda^{-1}+B_3\lambda\}$$. Drude model Refractive index and extinction coefficient are connected: $$2n(\lambda)k(\lambda)=\displaystyle\frac{A_1A_2\lambda^3}{\lambda^2+A_2^2}$$ $$n^2(\lambda)-k^2(\lambda)=A_0-\displaystyle\frac{A_1 A_2^2\lambda^2}{\lambda^2+A_2^2}$$ Hartmann model $$n(\lambda)=A_0+\displaystyle\frac{A_1}{\lambda-A_2}$$