I encountered some problems when simulating the reflectance/transmittance of ordered GaN Nanowire (NW) arrays. The NWs have a fixed diameter and length and are arranged in a periodic hexagonal lattice. Here i´m simulating over a unitcell containing 2 NWs with periodic BCs in the x and y direction and PML on the z axis.
The NWs are illuminated with a plane wave source (375-800nm) at normal incidence.
Now because the NWs behave like a grating there are some artifacts occuring at certain wavelengths, in dependence on the distance between the NWs, and the location of this artefact can be calculated before the simulation as shown here (DOI: 10.1021/nl200201b) which occours in my case at around 500nm Wavelength for a distance of 1000nm between the NWs.
Now to my Question:
Is there a way to reduce the error (which is exagerated by the FDTD algorithm) or in the best case remove it completly?
The problem is that it seems that the spectrum obtained before or after the artifact is not a continous function if you exclude the artifact in many cases. It looks more like a step which can extend over a range of ~100nm wavelength.
Thank you in advance for your time!
Reflection from above the NWs inside with the Source above the NWs. Here one can see the step from ~400-500nm.
Transmission from below the NWs inside with the Source inside the Substrate to the top. Here no step is visible and the function appears to be continous.