an angled plane wave with bloch boundary

fdtd

#1

i simulated a case that plane structure illuminated with a plane wave at an angle with bloch boundary.
but the reflectance was wrong, could you help me to check it.
plane_bloch.fsp (1.2 MB)


#2

The problem comes from the Bloch boundary condition: with a plane wave with non normal incidence, the angle varies with the wavelength (https://kb.lumerical.com/en/index.html?ref_sim_obj_broadband_injection_angles.html).

To avoid that, you can either run a sweep of single wavelength simulations over the bandwidth of interest, or you can used the BFAST plane wave (https://kb.lumerical.com/en/index.html?ref_sim_obj_sources_bfast.html).

Note that BFAST can lead to some stability issues with dispersive material. I ran your simulation using this setting, but I had to set the BFAST dt multiplier to 0.1 to get stability.


#3

thanks a lot