# Importing arbitrary dispersive models

This post describes how to implement dispersive models not directly supported by Lumerical Solutions. This example shows how you might create a Plasma + Lorentz model.

One option is to use the Analytic material model, which requires an analytic function to define the refractive index. See the Analytic material model page for more information. The second option, which we will consider here, is to evaluate the function with some other tool (eg. MATLAB) and use the Sampled data material model.

### Associated files

usr_create_dispersive.lsf (2.7 KB)

Note: Improve fit with advanced options