Simulation of photonic crystal waveguides to find band structure by COMSOL

Hi everybody,

I am trying to simulate a photonic waveguide using COMSOL. The geometry is more or less as mentioned in https://www.osapublishing.org/ome/abstract.cfm?uri=ome-7-1-43.

The point is that when I plot the dispersion curves they are all identical!!!!!!!!!!

Any idea how to simulate and get the correct band structure?

Best, Maryam