Reply To: Effective indices of first two modes in SWG

[Guilin Sun]

I do not understand why you change the wavelength range now. Please check.

Now it has two bands. The other one may be real or fake, which will need you to identify.

The First Brillouin zone gives you the max k vectors at the symmetry points. In other periodic structure with square lattice, the relative kx is from 0 to 0.5. However now it is waveguide so its range will be smaller. 

Please visit this link  https://optics.ansys.com/hc/en-us/sections/360006919074-Photonic-crystals to check how to simulate the band structure (methodology).