Negative permittivity of metals – light-trapping and plasmon

[shishi]

Negative permittivity of metals – The effect of light-trapping via plasmonics

I’m trying to understand the effect of light-trapping by plasmonics (for example - Localized Surface Plasmon Resonance, Surface Plasmon Polariton, Scattered Plasmons), and how negative permittivity related to that?

To the best of my knowledge, negative permittivity (ε) occurs when incident wave below the plasma frequency (ω_p) strikes a bulk metal. In this case, the free electrons can move in a way that cancel the incident wave, and the wave will reflected from the metal (mirror-like). If the frequency of the incident wave will be above the plasma frequency, the permittivity will be positive and the electrons cannot move in a way that cancel the incident wave, and the wave will penetrate to the metal.

ε=ε₀(1-ω²_p/ω²)

When people speaking about light-trapping (antenna-like) using plasmons, one of the critics is negative permittivity and I don’t understand how the light can be trapped (because it should we reflected, mirror-like)?

Any input on this matter will be highly appreciated :)

 

[tech99]

I wonder if you have seen the following paper:-
http://www.frdint.com/physics_of_electrostatic_resonance.pdf
It is about the trapping of EM radiation in meta materials with negative permittivity. But I am not sure if a homogenous piece of ordinary metal also behaves as a meta material at frequencies below the plasmon resonance.