Can someone please explain extraordinary optical transmission (EOT)?

Can someone please explain extraordinary optical transmission (EOT)?

I'm hoping someone can describe the physical process by which light is transmitted through a periodic metal hole array which is optically thick (i.e. thickness > skin depth), for which the holes are sub-wavelength vs the incident light. I'm trying to visualise how this process works but I'm not having much luck.

From what I understand, EOT is a mixture of surface plasmon polaritons (SPPs) being excited on the surface of the hole array and wave guided modes for the SPPs(?) to travel through to the opposite side of the array where they are decoupled into transmitted light. I guess it's the wave guided SPPs I'm having trouble with...i.e. why would there be a cut-off frequency due to the wave guide mode if SPPs travel along the metal surface? (Also, the position at which the SPPs would decouple has also been bugging me.)

Any help would be great!

The coupling from surface plasmon into transmitted light takes place at the edges of the holes. At each sharp edge, light scatters into many different $k$ vectors. Some of the $k$ vectors match those of specific modes, such as the surface plasmon modes, and the wave guide modes in the holes.