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Smallest of the Small?

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Science  14 May 2010:
Vol. 328, Issue 5980, pp. 811
DOI: 10.1126/science.328.5980.811

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Summary

Lasers have been shrinking ever since they were invented 50 years ago. But the 44-nanometer "spaser" will be hard to beat. The device is akin to a conventional laser, but in the surface-plasmon laser, or spaser, a conventional bluish-green laser beam is shined into a suspension of nanoparticles, each with a gold core surrounded by a layer of sodium silicate and an outer silica shell containing dye molecules. When the gold is excited by the laser photons, its surface starts to dance with collective oscillations of electrons, known as surface plasmons. The plasmons tickle the dye molecules to release more plasmons at the same wavelength, causing the device to emit green laser light.