Princeton researchers discover new typ...( A Princeton-led team of researchers ...)

A Princeton-led team of researchers has discovered an entirely new mechanism for making common electronic materials emit laser beams. The finding could lead to lasers that operate more efficiently and at higher temperatures than existing devices, and find applications in environmental monitoring and medical diagnostics.

"This discovery provides a new insight into the physics of lasers," said Claire Gmachl, who led the study. Gmachl, an electrical engineer, is the director of the Mid-Infrared Technologies for Health and the Environment (MIRTHE) center. The phenomenon was discovered in a type of device called quantum cascade laser, in which an electric current flowing through a specially designed material produces a laser beam. Gmachl's group discovered that a quantum cascade laser they had built generated a second beam with very unusual properties, including the need for less electrical power than the conventional beam. "If we can turn off the conventional beam, we will end up with a better laser, which makes more efficient use of electrical power," said Gmachl.

The team that conducted the study includes Gmachl's graduate student Kale Franz, who built the laser that revealed the new phenomenon, and Stefan Menzel, a graduate student from the University of Sheffield, UK, who unearthed the unique properties of the phenomenon during an internship at Princeton University last summer. The study was published online in Nature Photonics on Dec. 14.

The light emitted by a laser differs fundamentally from light produced by common sources such as the sun, fire, or electric lamps. According to the field of physics called quantum electrodynamics, light is made up of particles called photons. Common sources of light emit photons that are in a random order, like crowds milling about a busy marketplace. In contrast, photons in a laser are "in sync" with each other, like a music band marching in formation. This property, called coherenc
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