Dispersive 2nd-Order Nonlinear Material

Compatibility:

In this model, the electrical displacement D is

FDTD - equations 32

where εL is the linear relative permittivity and X(2) is the second order isotropic
susceptibility. They are the real values. In order to simulate second order nonlinear
effect, you should input two parameters: the linear relative permittivity  εL and the
second order isotropic susceptibility X(2).