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.