Energy-efficient laser works at room temperature

First practical polariton light source could improve medical devices

An energy-efficient alternative to the laser no longer requires a deep freeze. The first plug-in, room-temperature polariton laser, reported in the June 13 Physical Review Letters, could soon find its way into electronics and medical devices.

Traditional lasers work by stimulated emission, in which atoms energized by electric current emit light. In polariton lasers, light is emitted by polaritons, particle-like couplings of light and matter. While polariton devices will never produce laser beams powerful enough to burn through metal, their big selling point is that they require very little electricity.

Last year, two research groups reported building polariton lasers that ran on electricity rather than another laser. But both lasers worked only in near-absolute-zero temperatures (SN: 6/29/13, p. 16). Now one of those groups, led by electrical engineer Pallab Bhattacharya at the University of Michigan in Ann Arbor, has eliminated that restraint. His team uses a thin strip of gallium nitride along with mirrors and electrodes to preserve the short-lived polaritons and emit a weak beam of ultraviolet light. The device uses about 0.4 percent of the electricity of a comparable conventional laser.

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