The development is being disclosed today in the new issue of Nature, a scientific journal. Bell Labs scientists said the quantum cascade (QC) semiconductor laser is the first to emit light continuously and reliably over a broad spectrum of infrared wavelengths. The new device eliminated the drawbacks of previous attempts at producing broadband laser action, they said.

"An ultra-broadband semiconductor laser could be used to make an extremely sensitive and versatile detector that can detect minute traces of pollutants in the atmosphere," said Claire Gmachl, a physicist at Bell Labs. "It could also be used to produce new medical diagnostic tools such as breath analyzers."

Currently, semiconductor lasers are compact, rugged, and often portable, but they are also typically narrowband devices, emitting light of a single color at a characteristic wavelength, said Bell Labs. Ultra-broadband lasers offer major advantages in that they allow for sampling of a wide swath of wavelengths at the same time, said the research lab. This aspect of ultra-broadband lasers opens the possibility of producing a semiconductor device that is reliable and works under a wide variety of operating conditions--a goal for scientists for a long time, according to Bell Labs.

To fabricate the new laser, Bell Labs scientists stacked more than 650 different layers of standard semiconductor materials used in photonics on top of one another, said Lucent's the research unit. These layers are grouped into 36 stacks. Each stack has slightly different optical excitation properties and generates light over a short but characteristic wavelength range, while remaining transparent to the rest, Bell Labs said. Together the combined stacks produce broadband laser emission.

The new devices belongs to a class of high-performance semiconductor lasers called quantum cascade (QC) lasers, which were invented at Bell Labs in 1994. The QC laser operates much like an "electronic waterfall," with electrical current flowing through the device causing electrons to cascade down "an energy staircase," according to Bell Labs. Each step emits a photon of infrared light, and emitted photons are reflected back and forth inside the semiconductor resonator, which amplifies the output power, said the lab.

The ultra-broadband lasers emit 1.3 watts at peak power over the mid-infrared range of 6-8 micrometers, researchers said.

"The wavelength range can in principle be made much wider, or also narrower," Gmachl said. "We picked the range of 6 to 8 micrometer for laser action as a good range for a convincing demonstration of the idea. In the future, we may be able to custom tailor the laser to the specific needs of individual applications, including fiber optics."