Questions regarding Surface plasmons

[ppoonamk]

Hey

I am an undergrad student researching on surface plasmons. I have some queries regarding this

1)I would like to understand how the wavelength is shorter that the incident light when the frequency remains the same
2) I would also like to know how extraordinary transmission occurs

 

[josh_einsle]

Hi,

I am not sure if I understand the first question at all. could you please re-phrase?

as to point number two, EOT on thin metal films occurs through the coupling of several processes. The first one is that by periodically structuring a metal film a surface Bloch mode can be set up on one surface. Then these surface plasmons couple into the evanescent light propagating through the sub-wavelength aperture. (by the way the aperture actually has a effective size larger than the physical one due to the E field penetrating into the surface of the metal.) once the light propagates through the aperture it can then set up a second surface bloch mode on the other side of the thin film, which then de-couples out from the surface mode to produce far field light again.

There is a really good review article about this written by C. Genet and T.W. Ebbesen in Nature vol 445, pg 39. The references in there will be good as well. I would also recommend sitting down with the Stefan Maier book on Plasmonics. His exposition is quite clear.

 

[Kayacan]

Hey,

I am a new user in this forums.. I have a question concerned SPPs (Surface Plasmons Polaritons).. What are differences between internal damping and radiation damping in surface plasmons??

Can anyone response ? Thanks ..

Best wishes,
Kayacan, France

 

[josh_einsle]

quickly, radiation dampening could be thought of as loss of energy through the conversion back into light, where as internal dampening would be ohmic and other absorptive losses.

 

[Kayacan]

Thank you josh einsle...

Assume that we have a structure like that : glass + metal + air. I know that there are two types of SPPs. First one is propagates at the surface of metal (metal+air) and the second one is at the interface between metal and glass. Most of the researches interested in excitation first type SPPs. Why do not interested in second one?? It is better confined than the first one in terms of effective refractive index of metal+glass.
Does it have a disadvantage??

Many thanks..

Kayacan, France

 

[josh_einsle]

Thank you josh einsle...

Assume that we have a structure like that : glass + metal + air. I know that there are two types of SPPs. First one is propagates at the surface of metal (metal+air) and the second one is at the interface between metal and glass. Most of the researches interested in excitation first type SPPs. Why do not interested in second one?? It is better confined than the first one in terms of effective refractive index of metal+glass.
Does it have a disadvantage??

Many thanks..

Kayacan, France

Hi kayacan- I think it is a gross simplification to say that researchers are interested in on metal-dielectric interface over another. the metal/air interface presents one that is probably the most encountered in everyday experience, but if you were to look at the dispersion curve for this system you would see it is also pretty hard to excite SPP on this interface since the SPP curve is to the right of the light line. For this reason some sort of system to modify the lights momentum needs to be used. This usually comes in the form of, prisms for ATR induced coupling, or gratings. It is the 2nd type that have a lot of current (read past 10 years) literature on them since this is the type of system that sub-wavelength apertures comprise. As to better confinement, I would not be able to answer. I would say that metal/air will come up slightly more as this is how many people want to build the device, and not have to imbed it in a dielectric, though there are many applications for that as well.

j

 

[Kayacan]

Hey Josh Einsle,

Thanks you for your answer and interest to my curiosity. First of all, I am searching a reliable source or article (as a reference) to approfondir the excitation of second type SPPs (i mean that at the metal+glass ).

Secondly, in metal+air , there will be a leaky mode and that is not a disadvantage (as a radiative loss).

Thirdly, how can we excite second mode (at the interface SPP) indepently from the first one? Or is it possible ?


Best regards and I appreciate to your answers.

Kayacan

 

[josh_einsle]

I think you are still missing some basics since the excitation of SPP's on the air/metal is the same as glass/metal, just material specific conditions need to be meet.

I would suggest that you read Mair's book on plasmonics, and also look at Rather's classic and oft cited text.

Since i am not really following all of your questions, I will answer the third only as it is clear to me. If you have a optically thick metal surface on a glass substrate, then you could excite an SPP on that surface only as long as you meet the excitation conditions. This could be done by creating a series of grooves, that do not pierce the metal film for instance. Again I would review the references above so you can get a handle on the mechanisms for exciting SPPs.