Zap a metal with light and the electrons on the surface ripple
into waves ? known as plasmons ? which emit light of their own.
The frequency of that light reflects the electronic nature of
the surface and is highly sensitive to contamination. Kevin Tetz
and colleagues in the Ultrafast and Nanoscale Optics Group at
the University of California, San Diego, have designed a system
to exploit that to test for any surface contamination on the
surface of, well, anything. Their idea uses a thin layer of
metal drilled with nanoscale holes, laid onto the surface being
tested. When the perforated plate is zapped with laser light,
the surface plasmons that form emit light with a frequency
related to the materials touching the plate. A sensitive light
detector is needed to measure the frequency of light given off.
The team says devices using this approach can be small and
portable, will work on very low power, and could detect
everything from explosives to bacteria. All that needs to be
done now is build a system able to