Surface plasmon resonance (SPR) occurs when light (incident from top of video in a prism - n=1.5) excites outer shell electrons of a metal film (50 nm silver film in this video). This simulation is done with violet light (a wavelength of 400 nm). As the angle of incidence increases from 0-80 degrees, light has enough horizontal momentum to excite propagating surface plasmon polaritons (SPPs) at ~50 degrees with maximum resonance at 60 degrees. SPPs can be seen on the bottom of the silver film (in air - n=1). This simulation is done in Comsol 5.0.
![](https://s2.save4k.ru/pic/OMzeARbhjC4/mqdefault.jpg)