Nonlinear Optics not converge

Hello everyone,

I am trying to use Comsol to simulate a nonlinear optics problem using in the frequency domain. More specifically, I use n=n_0+gamma*power as the form to include third nonlinearity. Comsol can handle the simulation when nonlinearity is not very strong (\Delta_n=gamma*power<0.01), but when the nonlinearity is increased, Comsol cannot converge. Anyone has met similar problem, and could you guys give me some suggestions?

Thanks!