Researchers develop simplified approach for high-power, single-mode lasers

August 24, 2012

(—When it comes to applications like standoff sensing—using lasers to detect gas, explosives, or other materials from a safe distance—the laser's strength is of the utmost importance. A stronger and purer beam means devices can sense danger more accurately from a greater distance, which translates into safer workers, soldiers, and police officers.

Northwestern University researchers have developed a new resonator that creates the purest, brightest, and most powerful single-mode quantum cascade lasers yet at the 8-12 micron range, a wavelength of great interest for both military and industrial use.

A paper describing the findings, "Angled Cavity Broad Area Quantum Cascade Lasers," was published August 21 in the journal Applied Physics Letters.

in the 8-12 micron range is of interest for military and industrial use equally, as almost all chemicals (including nerve gases and toxic industrial chemicals) can be identified by infrared absorption in this range. In addition, the atmosphere is relatively transparent in this , which allows for sensing from a distance.

But to be successful, standoff sensing applications require that laser sources be high-powered, single-mode, and possess good beam quality. Incorporating all three qualities in a single device is a significant challenge, and many sophisticated structures have been proposed with little success.

Manijeh Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science in the McCormick School of Engineering and Applied Science, and her group have created a new laser technology that controls both wavelength and beam quality. The feat is achieved through the use of a new type of "distributed feedback" mechanism called Β-DFB, a simple diffractive feedback in an angled laser cavity.

"Our is the most promising device for creating high-power, single-mode laser sources with good beam quality, and it is inexpensive and can be realized at room temperature," said Razeghi, who leads the Center for Quantum Devices (CQD). "Furthermore the design can be applied to a wide range of semiconductor lasers at any wavelength."

Razeghi and her group demonstrated >6 watts of peak power with nearly diffraction-limited beam quality at a wavelength of 10.4 microns—the highest power single-mode semiconductor laser demonstrated at a wavelength greater than 10 microns. Refinement of the design, particularly related to optimization of the cavity design and improvement of the gain medium, are expected to increase the output power significantly.

The development of the Β-DFB is complementary to active research efforts within CQD, but is not yet directly funded.

Explore further: Laser sets records in power and energy efficiency

Related Stories

Building a more versatile laser

November 16, 2009

( -- One of the drawbacks associated with using semiconductor lasers is that many of them can only produce a beam of a single wavelength, and can only send that beam in one direction at a time. There have been ...

New VECSEL could mean a step forward for spectroscopy

October 25, 2010

( -- "Unfortunately, for spectroscopy, the beam quality of quantum cascade lasers is not satisfying," Hans Zogg tells "We are developing lasers for the mid-infrared range which have an especially ...

Recommended for you

Perfectly accurate clocks turn out to be impossible

October 7, 2015

Can the passage of time be measured precisely, always and everywhere? The answer will upset many watchmakers. A team of physicists from the universities of Warsaw and Nottingham have just shown that when we are dealing with ...

The topolariton, a new half-matter, half-light particle

October 7, 2015

A new type of "quasiparticle" theorized by Caltech's Gil Refael, a professor of theoretical physics and condensed matter theory, could help improve the efficiency of a wide range of photonic devices—technologies, such as ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.