| Topic: |
Science > Physics |
| User: |
"Sam Wormley" |
| Date: |
23 Mar 2006 01:30:45 PM |
| Object: |
Surface plasmons squeeze light |
Surface plasmons squeeze light
http://physicsweb.org/articles/news/10/3/17/1
The backbone of the world's communication system is a network of
optical fibres that carry information in the form of light pulses.
Large volumes of data can be transmitted very efficiently down these
fibres but bottlenecks in the system occur when the light pulses are
converted into electrical signals at various "junction boxes" that
ensure information reaches its correct destination. The
telecommunications industry, among others, is therefore extremely
interested in microphotonic circuits that can manipulate light pulses
directly and therefore increase data rates.
Physicists in Denmark and France led by Sergey Bozhevolnyi of the
University of Aalborg have developed a new class of waveguide that
could get round one of the biggest obstacles to photonic circuits. The
devices allow light at telecommunications wavelengths to be "squeezed"
to below the diffraction limit, allowing it to pass though small
regions such as channels on a chip without being significantly lost
(Nature 440 508).
Diffraction means that only a tiny amount of light can pass through a
hole that is narrower than the wavelength of the light, and the light
that is transmitted emerges in all directions. This can be problematic,
for example, in optical lithography where diffraction prevents the
fabrication of semiconductor features below a certain size. In
telecommunications, where the light typically has a wavelength of 1.5
microns, light cannot pass though the channels used to guide electrons
in today's silicon chips because they are too small.
One way to overcome this problem is to use light waves to excite the
collective wavelike motions of billions of electrons on the surface of
metals. Unlike the light waves themselves, these "surface plasmons" are
not restricted by the diffraction limit of light. Indeed, Bozhevolnyi
and co-workers previously showed that the plasmons can be used to guide
light through grooves in gold that are much narrower than the
wavelength of the light used.
See: http://physicsweb.org/articles/news/10/3/17/1
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