Metamaterials Absorption Loss Problem Solved
Diagram of experimental setup, Credit: Noginov et al.
Metamaterials are engineered media that have many unique electromagnetic properties. Among these exotic properties is the possibility of a negative index of refraction, while most materials have a positive index of refraction. This leads to several interesting implications:
The doppler shift is reversed
Wave fronts move opposite to the flow of energy
Snell’s law is reversed
Because of these unusual properties, several potential applications have been proposed, such as
Optical Cloaking
Nanolasers
Subdiffraction resolution imaging (very precise microscopes)
However, most metamaterials constructed this far have been fundamentally limited by the amount of absorption loss they exhibit. This means that most of the light does not make it through, rendering these metamaterials unsuitable for application. Recent publications have shown that one solution to this problem is to add a dielectric material with an optical gain adjacent to the metamaterial [1]. However, this wasn’t experimentally verified until now.
Just published in Physical Review Letters is a paper entilted Stimulated Emission of Surface Plasmon Polaritons by M. A. Noginov et al. In it they report upon the experimental observation of compensation for absorption loss via stimulated emission of surface plasmon polaritons.
Surface plasmon polaritons are quasiparticles generated by the coupling of light with surface plasmons. Surface plasmons are quantum of plasma oscillations, analagous to the quantized portions of light called photons, that are confined to the surface of a material. When these surface plasmons interact with light, they create the polaritons. These polaritons, described by Noginov et al as “electromagnetic waves coupled to oscillations of free-electron plasma,” are emitted at optical frequency. This is the mechanism utilized for optical gain in the adjacent dielectric.
They conclude their paper by saying, “The demonstrated phenomenon adds a new stimulated emission source to the toolbox of nanophotonic materials and devices..” Not only does this experimental demonstration allow the possibility of future applications of metamaterials to take advantage of the previously mentioned properties, but it has significantly improved understanding fo the proposed theories behind the phenomenon. For more information, see the paper listed below [2].
Sources:
[1] I. Avrutsky, Phys. Rev. B 70, 155416 (2004).
[2] M.A. Noginov et al, Stimulated Emission of Surface Plasmon Polaritons. PRL 101, 226806 (2008).
This entry was posted on Wednesday, December 3rd, 2008 at 8:08 pm and is filed under Atomic, Molecular, and Optical. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
