Boundary conditions for electromagnetic waves

Dear comminity,

Can you help me with the following:

What should be the boundary conditions if my wave changes its polarisation during the propagation from linear to elyptically - polarised? I suppose ports will not work, because we should define the polarisation of the wave, but in my case it can vary.

I tried PML, but it doesn`t work properly.

So I have a linear - polarised plane wave that is propagating through anisotrpic medium and changes its polarisation to elyptic.

Thanks for help!