i am working on nonlinear phenomena in photonic crystal for design an optical isolator based on cavity coupled to waveguide in photonic crystal slab based on InP. the linear simulation is correct but the nonliear simulation does’nt work properly.the electric field intensity in structure is high and sufficient for excite kerr effect but the result not change (transmission must be shifted).lattice cst 447.fsp (3.9 MB)

# nonlinear waveguide_cavity coupled photonic crystal

**fgomez**#2

Hi Hossein,

Sorry for the long wait, I will look at your file and post some comments and suggestions as soon as possible.

**fgomez**#3

Dear Hossein,

The amplitude you are using in the source settings is 1 (see below).

This means the electric field has an amplitude of 1 V/m, which is too small to excite the nonlinearity. For comparison, in the Kerr effect examples in the Knowledge Base we use amplitudes above of ~1e5 and ~1e9:

Spatial solitons: https://kb.lumerical.com/en/index.html?other_application_spatial_solitons.html

Kerr effect: https://kb.lumerical.com/en/index.html?nonlinear_kerr_introduction.html

For the nonlinearity to have a significant effect the product of the chi3 coefficient and the square of the amplitude should be smaller than 1 so that the nonlinearity does not cause a divergence (see the methodology for nonlinear simulations) but not too small that the effect is negligible. For example, in our Kerr efect example we use a chi3 of order 1e-21 and an amplitude of order 1e9 so the product chi3*E^2 is of the order 1e-3.

**david.soheil**#4

for an chi3 of x^(3) = 4.8 * 10^-10 esu, the SI unit is 3e-20 ?!

I’ve confronted with some problems on account of lumerical units!

I’ve The signal intensity of 1.9 * 10^4 V2/m2 . now in lumerical I only see the amplitude of the input signal. how am I suppose to add it as it is!?