Dear Lumerical technical support,
I followed examples from https://kb.lumerical.com/en/diffractive_optics_waveguide_pcbandstructure.html
and design a slab photonic crystal with square lattice. Having modified the script now I scan the entire bandstructure and create find large bandgap at large frequency range.
1.Then I build a line defect photonic crystal waveguide and butt coupler and it works well for 1.5-1.6um.
However it does show transmission oscillation at ~ 1.3um if source bandwidth covers that and at that wavelength there should also be a bandgap. Why this can happen?
2.I am using such photonic crystal waveguide only at 1.5-1.6um and try to create a sharp bend. However a 90 degree bend shows strong reflection and scattering inside lattice and transmission is very low.
However it seems from other software like COMSOl with following link: FEM results did not sow such reflection
2.5d bend1.lms (432.1 KB)
2.5d straight.lms (430.9 KB)