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Field distribution calculations and the correct thickness and location of PML layer.

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Dear all

I am trying to calculate the field distribution of metallic grating, the structure consists of Ag layer on top of SiO2 substrate. On top of the Ag layer I have the grating and on the top I have Air (Superstrate). Please see the attached picture in which I show the structure and all the dimensions (in fact the structure is in 3D but I showed you a cross section, I know that I can build it in 2D but for some reason I need to build it in 3D). In this structure I am interesting to calculate the electric field distribution as well as the field enhancement factor of the electric field. I solved a full field problem. My questions are:

1. I have used electric field boundary to excite the structure because when I used a port I got a strange (very large ~10^8 ) V/m)) values of the electric field (the amplitude at the input is one (V/m), is it correct to use electric field boundary to excite the structure in this case? because i think the use of port is good when I want to calculate the reflection from the structure for example.

2. The second question which is important is about the PML layer. I used two PML layers, one on top of the Air domain (the material of the PML is Air) and the other is located at the bottom of the SiO2 (the material of the PML is SiO2). I don't know why the results depend on the location (relative to the grating for example) and the thickness of the PML layers. How can I find the correct location and thickness of the PML. Now it is located around one lambda above the grating !!!
I am using Comsol 5.0.
Thank you all in advnance
Mohammad


1 Reply Last Post Apr 18, 2016, 5:16 a.m. EDT

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Posted: 9 years ago Apr 18, 2016, 5:16 a.m. EDT
I am using Comsol 5.0.
I am using Comsol 5.0.

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