What Are Surface Plasmons and How Do They Relate to Maxwell's Equations?

[alexyan]

what is "plasmonic resonance"

hi, could somebody who is familiy with "plasmonic resonance" tell me about it?

thank you!

 

[El Hombre Invisible]

Sorry. No relation of mine.

 

[Claude Bile]

Surface Plasmon resonances are found on metal/dielectric interfaces.

A surface plasmon resonance manifests itself as a sharp dip in the reflectivity of a metal surface when varying the angle of incidence. This is because the energy of the incident wave, rather than being reflected, is coupled into surface plasmon modes that propagate along the surface of the metal.

There are also bulk plasmon resonances that occur within the volume of the metal itself, although I am not as familiar with this type of resonance.

Claude.

 

[Danger]

Hi Claude;
Does this occur within the visual spectrum? I've noticed that sometimes metal is difficult to look at without getting a headache because I can't seem to focus on it. It would be a lot more dignified if there were a physical cause as opposed to me just being nuts. (I am nuts, of course, but that's totally beside the point right now.)

 

[dgiznya]

plasmons

Plamons do occur in the visible.

Think of the free electrons in a metal sloshing about like water in a bucket.
If you shine tunable monochromatic light on the metal and scan the wavelength, at certain frequencies(wavelengths) there can be a collective excitation of these free electrons.(absorption). This is what is known as a plasmon resonance.

 

[Claude Bile]

Surface Plasmon Resonance also commonly occurs in the visible. The neat thing about SPR is that the resonance frequency is very sensitive to the refractive index of the dielectric layer on top of the metal layer, making it a very simple way of measuring subtle refractive index changes in fluids for example.

You wouldn't notice this effect though by just looking at metal though since the spectral dip is quite narrow.

Claude.

 

[alexyan]

Hi, Claude,
Thank you for your helpful reply. I do not understand how "Surface Plasmon Resonance" still can propagate along the interface. my understanding is when Resonance happens energy will stop transmiiting since plasma absorb and release energy. am I right?

 

[marlon]

hi, could somebody who is familiy with "plasmonic resonance" tell me about it?

thank you!

you are referring to plasmons , right ?

marlon

 

[Claude Bile]

Surface Plasmons are solutions to Maxwell's equations for metal/dielectric interface. Surface Plasmons also satisfy the wave equation, hence they are also propagating solutions to Maxwell's equations. In addition to this, they are also bound solutions in some cirumstances (much like the fields in an optic fibre for instance).

Surface Plasmons consist of two evanescent fields on either side of the interface. These plasmons propagate along the surface of the metal, however they still undergo absorption, diffraction etc.

Claude.

 

[marlon]

Surface Plasmons are solutions to Maxwell's equations for metal/dielectric interface.

I am just wondering about this definition. I just wanted to make a little remark, so i am not saying this definition is wrong or anything.

In college i was introduced to plasmons within the context of many particle-physics. I learned about the use of quasiparticles and it is within this context i encountered plsamons. So basically a bit like the Wikipedia presentation of plasmons.

So plasmons are quasiparticles (ie particles + their interactions = quasiparticles that yield uncoupled differential equations to describe the dynamics). Morespecifically the particles here are (conduction-)electrons and the interaction is between the electrons and some incident EM-wave(photons). If the electric field has a certain frequence the above denoted electrons will jointly move back and forth as a respons to this E-field. In other words these electrons form an oscillation of charge carriers. This oscillaton is quatisized and the resulting "particles" are plasmons (just like the phonons are particles associated with lattice vibration quantization).

Once this is introduced, you get the story of the plasma frequence and the optial properties of metals (ie the screening of the incident -field by the joint motion of the conduction electrons)...


My question is how surface plasmons are solutions of the Maxwell equations ? I mean, what about the electrons being described by the QM ? The way i see it, the EM-part of plasmons only arises in the incident EM-field but in the actual interaction with electrons and after that, the quantization of the resulting plasma-oscillations (the joint oscillatory motion of the electrons as a response to the incident EM-field) which we call plsamons, requires a whole lot more

regards
marlon