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New laser system: Short pulses promise big benefits

New Mexico State University researchers now have on-campus access to a new type of laser system that many believe could lead to technological breakthroughs in fields ranging from medicine to antiterrorism.



David Voelz of NMSU's Klipsch School of Electrical and Computer Engineering, left, and chemistry professor Gary Rayson are among the NMSU researchers who will use the Raydiance ultra-short-pulse laser system. (NMSU photo by Darren Phillips)

With help from the Governor's Office, the university has installed an ultra-short-pulse (USP) laser system developed by Raydiance Inc. that is small, easy to use and reliable.

Unlike conventional continuous-wave lasers, USP lasers emit "very short, compact bundles of energy," said chemistry professor Gary Rayson, one of the principal investigators leading the USP laser project at NMSU.

Until now, typical USP lasers have been large, complex and temperamental set-ups, Rayson said. The Raydiance unit is about the size of a small microwave oven, it runs on a standard 110-volt power supply, and the software developed for operating the system is user-friendly.

The Raydiance system emits pulses of about two picoseconds - that is, about two trillionths of a second. Such brief pulses offer great precision for applications such as eye surgery or etching microchips - microscopic bits of material can be ablated, or vaporized, without causing heat damage to surrounding material as conventional lasers do.

NMSU researchers - from chemistry, biology, electrical engineering, physics and geology - are lining up to explore the laser's potential in other applications.

"What I'm interested in is using the laser for nonlinear spectroscopic measurements as a means of detecting trace amounts of biological, chemical and explosive materials," Rayson said.

David Voelz of the university's Klipsch School of Electrical and Computer Engineering, co-principal investigator on the project, wants to evaluate the laser's potential in diffusion tomography, a method of imaging objects that are obscured within a turbid medium - like a tumor within the human body or a vehicle in clouds or turbid water. Diffusion tomography requires short pulses of light to enter the medium and time-resolved photo detection of the scattered photons to create an image.

Biologist Elba Serrano is interested in using the laser to develop applications for live imaging of neural and sensory tissue for biomedical applications. Geologist Nancy McMillan will use it for spectroscopic analysis of rock and mineral composition, including gems, where minimal destruction is important.

For physics professor Robert Armstrong, who is developing sensors based on a type of laser spectroscopy known as surface-enhanced Raman spectroscopy, the ultra-short pulses of the Raydiance laser should offer greater sensitivity, less degradation of the metal substrates used to enhance the signals, and minimal damage to the target.

Rayson's work also utilizes Raman spectroscopy, which analyzes the scattering of light caused by the interaction of the laser beam and the molecules in the target. Because of the complex laser systems required, advanced variations of Raman spectroscopy have been "relegated almost to a priesthood of laser spectroscopists," Rayson said, but the advent of the Raydiance system "may be the breakthrough that would bridge the gap between the purest academic lab and real-world applications."

Getting the equipment into the hands of researchers is the key to identifying those applications. In New Mexico, the Governor's Office is facilitating that process by providing the support for each of the state's three research universities to lease a Raydiance laser system.

"When Raydiance came to the state with a plan to couple the scientific talent we have in ultra-short-pulse lasers with a robust but flexible laser platform, we saw a great opportunity for the state to become a national leader in high-tech applications of ultra-short-pulse lasers," said Thomas J. Bowles, science adviser to Gov. Bill Richardson. "This is a field that promises to be a revolutionary technology that will spawn entirely new areas of business. This is a great example of how the state can support R&D that will lead to strong economic growth in New Mexico."