I am trying to replicate the diffraction grating filter response (at least the transmission) from the following paper (Fig. 2 of the paper) :
Particle swarm optimization and its application to the design of diffraction grating filters
Here is my lumerical file:
diffraction_grating_filter.fsp (275.2 KB)
Now I think I can get the correct wavelength at which my transmittance is lowest (reflectance is high) but my filter does not have a sharp cutoff as the one shown in the figure.
Can anyone help me in debugging as to what I might be doing wrong? Here is the transmission plot that I am getting: