New book gives an overview of the applications

Apr 27, 2007 10:09 GMT  ·  By

Dr Stefan Maier, member of the Centre for Photonics and Photonic Materials at the University of Bath Department of Physics, wrote a 250-page book called Plasmonics: Fundamentals and Applications describing the basics of plasmonics.

The plasmon is the quasiparticle resulting from the quantization of plasma oscillations. They are a hybrid of the electron plasma (in a metal or semiconductor) and the photon. Thus, plasmons are collective oscillations of the free electron gas at optical frequencies, basically just an oscillation of the conduction electrons in a metal.

In plasmonics, light signals are sent down the surfaces of small metallic nanostructures. This makes it possible to create light circuits that are much smaller than those that can be made with insulating materials such as glass, the backbone of fiber-optic communications.

Plasmons play a large role in the optical properties of metals. Light of frequency below the plasma frequency is reflected, because the electrons in the metal screen the electric field of the light. Light of frequency above the plasma frequency is transmitted, because the electrons cannot respond fast enough to screen it. In most metals, the plasma frequency is in the ultraviolet, making them shiny (reflective) in the visible range.

On the other hand, some metals, such as copper, have a plasmon frequency in the visible range, yielding their distinct color. For other metals, such as gold, the plasma frequency lies deeply in the ultraviolet, but geometric factors come into play, which reduce the plasmon frequency to the visible. In doped semiconductors, the plasma frequency is usually in the infrared.

The new plasmonic devices could pave the way for computer chips that transmit and process information using light instead of electrons, with vastly improved computing speeds.

This offers the promise of computers that are much more efficient than today's machines, which have developed rapidly as microchips have been made smaller. But this process is due to end shortly because the laws of nature create a natural limit to electronics.

Plasmons have been considered as a means of transmitting information on computer chips, since they can support much higher frequencies (into the 100 THz range, while conventional wires become very lossy in the tens of GHz). They have also been proposed as a means of high-resolution lithography and microscopy due to their extremely small wavelengths. Both of these applications have seen successful demonstrations in the lab environment. Finally, surface plasmons have the unique capacity to confine light to very small dimensions which could enable many new applications.