By J.R. Wilson
MURRAY HILL, N.J. — The world's first ultra-broadband semiconductor laser has been announced by Bell Labs, the research and development arm of Lucent Technologies.
Potential applications for the new device, which is capable of emitting light continuously and reliably over a broad spectrum of infrared wavelengths, range from advanced optical communications to sensitive chemical detectors.
"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," says Bell Labs physicist Claire Gmachl.
A prime application of that capability would be aboard manned spacecraft, such as the International Space Station.
She also says the technique used to produce the new laser could be the basis for future high-performance semiconductor lasers for fiber optics and other technology applications, such as super-fast data transmission.
That technique involved stacking more than 650 layers of standard photonics semiconductor materials into 36 stacks, each with slightly different optical excitation properties. Each stack generates light over a short but characteristic wavelength range, while remaining transparent to the rest. Combined, the stacks produce a broadband laser emission.
The new device is an extension of the quantum cascade (QC) class of high-performance semiconductor lasers invented at Bell Labs in 1994. In a QC laser, electrons cascading down an energy "staircase" emit photons of infrared light, which are reflected back and forth within the semiconductor resonator that contains the cascade, stimulating the emission of other photons and enabling high output power.
The ultra-broadband laser emits 1.3 watts at peak power over the mid infrared range of 6-8 micrometers (a micrometer is one-millionth of a meter or roughly one-hundredth the diameter of a human hair.)
"The wavelength range can in principle be made much wider or also narrower," Gmachl says. "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."
