Applied Physics

What a Whopper

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Science  16 Oct 2009:
Vol. 326, Issue 5951, pp. 341
DOI: 10.1126/science.326_341b

The basic design of a laser sandwiches a gain medium between two mirrors. As the light bounces between the mirrors, the intensity of the electromagnetic field builds up within the cavity and spills out from one of the mirrors. Laser instrument size can vary greatly, from the tiny semiconductor devices in DVD and CD players, to the tabletop-confined systems used in spectroscopy and other laboratory applications. Then there are the football field–sized instruments used to probe high-energy light/matter interactions in attempts to harness the class of fusion energy released by the Sun. Reaching an even greater size scale, Turitsyn et al. present a fiber laser with a cavity 270 kilometers long. Such an ultralong laser could be used in secure communications. Because the properties of the waves building up within the medium depend on how the light bounces off the mirrors, a given protocol between a sender and receiver for manipulating the mirrors could provide mode selection for securely relaying messages.

Phys. Rev. Lett. 103, 133901 (2009).

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