MMI waveguide design...using PML

Hi,
I'm new to COMSOL, attended one of the workshops and have been going thru the tutorials.
I'm trying to design a slab waveguide...with a core refractive index of 3.48...cladding of 1.54....about 10um wide...and about 0.5mm long...input port (1um wide) at z=0...output port (1um wide) at end z=0.5mm...and using PML to enclose d waveguide
I want to find the ratio of output to input power (S21) for a particular freq/wavelength. Also, to be able to view the power distribution inside the waveguide...via some colour code, like in photon design ....
PLEASE HELP ME


Thanks,
Chuks.