Charge Perturbation Specification

tidy3d.LinearChargePerturbation	Specifies parameter's perturbation due to free carrier effects as a linear function of electron and hole densities:
tidy3d.CustomChargePerturbation	Specifies parameter's perturbation due to free carrier effects as a custom function of electron and hole densities defined as a two-dimensional array of perturbation values at sample electron and hole density points.