NonlinearSusceptibility

Model for an instantaneous nonlinear chi3 susceptibility. The expression for the instantaneous nonlinear polarization is given below.

$P_{NL} = \varepsilon_0 \chi_3 |E|^2 E$

Nonlinear Susceptibility

chi3: Chi3 nonlinear susceptibility.

Type: floating-point number

• Unit: μm²/V²
• Default: 0

Number of Iterations

numiters: Deprecated. Tidy3D ignores this value and uses the Iterations setting of the nonlinearity specification instead. The editor does not show this field.

Notes

• This model uses real time-domain fields, so $\chi_3$ must be real. For complex fields (e.g. when using Bloch boundary conditions), the nonlinearity is applied separately to the real and imaginary parts, so that the above equation holds when both $E$ and $P_{NL}$ are replaced by their real or imaginary parts. The nonlinearity is applied to the real and imaginary components separately since each of those represents a physical field.
• Different field components do not interact nonlinearly. For example, when calculating $P_{NL,x}$, we approximate $|E|^{2}\approx|E_x|^{2}$. This approximation is valid when the $E$ field is predominantly polarized along one of the x, y, or z axes.