# 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.

So at each edge, free radiation, surface plasmons, and wave guide modes, all convert a small fraction of their energy into each other.

(This paper explains some of the details, but unfortunately it is behind a paywall. I wrote some code based on the model in that paper, which you are welcome to examine, but it won't really help you understand the physics.)

• Thanks again @ptomato ! I'll have to work my way through it but that paper looks really usefull, cheers!
– Sean
Commented Aug 10, 2015 at 15:07
• I would be interested to know your thoughts on this paper or some others like it which suggest that EOT is dominated by diffraction and not surface plasmons?
– Sean
Commented Aug 10, 2015 at 15:18
• That paper is also behind a paywall. But my thoughts on the matter are that diffraction and surface plasmons are the same thing, in the end. Diffraction at the edges causes some light to enter a surface plasmon mode. Commented Aug 11, 2015 at 4:39