comsol 3D waveguide simulation

I am trying to simulate nonlinear optical effects in a 3D waveguide using "3D transient wave propagation" module in Comsol. Using "2D perpendicular propagation" module, I have already calculated the field distribution in linear regime of the particular guided mode that I want to simulate.

Now the problem is I do not know how to tell the 3D transient propagation module of Comsol to accept as boundary condition the field distribution already obtained in the linear analysis by 2D perpendicular wave propagation module. Unfortunately, I do not have any analytical expression which I could easily put in as demonstrated in the model library for the case of a gaussian wave propagation in 3D waveguide.

Can anyone help me on how we can define the boundary condition using numerical data already obtained? I should be happy if I could use results obtained either through Comsol or Matlab, whichever is easier.

Thanks in anticipation.

You'd better upload your model here.
why don't you do your linear simulation in 3Dmodule?