Supercontinuum laser emits from 2 to 2.5 microns at a 25 W output, 50 W coming this year

Ann Arbor, MI--A thulium-doped supercontinuum (SC) laser containing a fiber amplifier, created by Mohammed Islam, a professor of electrical engineering and computer science and biomedical engineering at the University of Michigan, and his team, emits 25.7 W in the 2 to 2.5 μm range. This is on the short-wavelength end of the so called spectral fingerprint region, which contains vibrational excitation lines of the all-important organic compounds.

The team includes researchers from the University of Michigan, Omni Sciences (Dexter, MI), SAIC (Arlington, VA), Air Force Research Labs (Wright Patterson Air Force Base, OH), EOIR Technologies (Fredericksburg, VA), Booz Allen Hamilton (McLean, VA), and the National Geospatial-Intelligence Agency (Springfield, VA).

The SC laser is nearly diffraction-limited (beam quality M² of better than 1.2) for all output power levels. The laser's spectral-output shape has stayed almost constant even as it has been scaled from 5 to 25 W; this makes it an excellent candidate for further scaling. The system is made of off-the-shelf telecommunications technology.

"For the defense and intelligence communities, this could add a new set of eyes," says Islam. The military already uses spectral fingerprinting to identify targets today to a certain extent, Islam notes. But it relies on the sun for the light, which can be a problem on a cloudy day or at night. While broadband IR lasers do exist, this one is more powerful, Islam says. And his group is now working on a 50 W prototype scheduled to be field-tested later this year.

Analyzing chemicals at airports
Beyond military applications, this device has the potential to improve upon today's full-body airport screening technologies. "Those are imaging devices looking for bumps where there shouldn't be bumps," says Islam. "They're looking for shapes that are odd or different. But they can't see the chemicals in the shapes. That's why you have to take your shoes off. But our laser can detect the chemical composition."

Omni Sciences has licensed Islam's technology from the University of Michigan. Islam has a financial interest in this company. The work was funded through a contract with the Air Force Research Laboratory.

A paper on the research is published online in Optics Letters and will appear in the July print edition. For more info, see http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-38-13-2292