Hello,

I am working on a dielectric metasurface mirror, where the reflection is applied by a 20nm gold surface. The reflectivity of the surface alone appears to be ~83% in the simulations for 850nm wavelength. When there are SiN dielectric material on top of the gold (periodic BC on sides, so the given structure is the 2D unit cell), R starts to depend on the dimensions of the material, where I’m varying its width and length for a given height and unit cell length. The dimensions I went for is 175nmx390nm. However, for this case, R goes down to ~58% and transmission becomes 26%, so there exists a significant loss in the gold and T is larger than the gold surface itself. I believe this might be a simulation issue, because I would not expect this much loss and also the results depend on the simulation settings (eg mesh level, mesh refinement, pml profile) too much. I could not diagnose the problem and hoping you could help me with it. Thank you very much.SiN_rect.fsp (3.1 MB)