Absorption monitor issue - plasmonic nanograting
I am trying to simulate a 1D metallic grating of Silver, over a double layers of silicon nitride and oxide, 11 nm and 5 nm, respectevely. The metallic nano grating is embedded in a PMMA passivation to avoid silver oxidation and the device is placed on 3um of Si. Schematic rapresentation of the strcuture in figure 1.
The purpose of the simulation is to evaluate the ART and the E and H fields in the device in the range (450-1100) nm.
Evaluating the absorption in the metal, I noticed some intensification of the field near to the borders of the metal (1or2 orders of magnitude more than the field inside the metal), figure 2.
The field in figure 2 is evaluated at the wavelength at which a peak is present (550nm). In figure 2.2 and 2.3 the same abs metal monitor but with the max of the colorbar scale set respectevely at 1 and 2 orders of magnitude lower than figure 2.
I have a issue also with the absorption in the silicon in the first tens of nm. It seems like the mesh is not able to accomodate a so strong field gradient, and this does not change with a more finer mesh (0.5nm), figure 3.
After every simulations, I performed some sanity checks:
- A+R+T=1, ok
- Doubling the mesh, ok
- Auto-shutoff ending, ok
I attached my simulation file,
I will appreaciate any helps.