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We need to use prism-coupling (e.g. Kretschmann or Otto configuration) or use grating to excite surface plasmon between metal and dielectric. What I understand is that when we use a grating or introduce some defects, some of the scattered wave satisfy the dispersion relation of SPP, and so SPP is excited. When SPP is excited, what is the actual $E$-field patterns that I observe in experiments or simulations?

I am trying to model this phenomenon in COMSOL as part of a bigger project, and I found the a powerpoint slide about this. The presenter used a plane wave on the flat metal surface to get the background E-fields (E1) in the first simulation, and the do the second simulation with the actual grating/defect with the result from the first simulation as input, and solve for the scattered field.

The first picture in the slide should be the fields ($E1$) due to the incident wave and the reflected wave from the plane metal surface, forming a standing wave pattern. (correct me if I'm wrong) What are the fields shown in the slide for the second simulation with the nice SPP profile? Is it the total fields ($E2$) in a metal-dielectric interface with the grating present, or is it $E2-E1$ (difference between the 'real' fields and the input plane wave)?

I'm not sure if this is just a specific question about computational EM with COMSOL. What I want to know is that in an experiment (or a computer simulation), if we launch a wave (e.g. laser) to a metal-dielectric interface with grating, what is the $E$-field profile.

enter image description here

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    $\begingroup$ have you considered shooting the author of the presentation an email with these queries? $\endgroup$
    – Kyle Kanos
    Jul 27, 2019 at 2:59

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The scattered wave is not important. You are after the surface plasmon polariton (SPP) mode, which is the wave propagating along the metal-dielectric interface. Since you are using COMSOL, you can easily find this E-field profile by using the Mode Analysis study option. In an experiment, it is extremely difficult to measure the actual E-field profile. You need to use a very sensitive near-field probe to do that since the SPP is highly confined to the metal surface.

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  • $\begingroup$ my question is that in reality do I actually get a clear SPP pattern as shown in the bottom figure, or is the SPP E-field actually 'hidden' in the background field as shown in the upper figure since not all the incident E-field is coupled to the SPP mode? $\endgroup$
    – Physicist
    Jul 27, 2019 at 23:17

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