Physics Professor Leads Innovations in Laser Technology

By Peter Grennen

These days, a description of the laser technology landscape can sound like something out of a war diary: The more commonplace lasers become, the greater the risk that a stray beam will hit an unintended target--a human eye, for instance. And yet the usefulness of lasers and their reputation for precision have effectively disarmed calls for better safety measures.

Owing to the work of Professor Gopal Rao, all that may soon be a thing of the past. Rao and a team of photonics researchers in the Physics Department's "laser lab" have unveiled a product that will surely make viewing lasers a much safer proposition.

Today, some forty years after the world's first laser beam was produced, lasers are found everywhere--from industrial tasks like welding, to medical uses like surgery, to children's games containing laser pointers. "Whether it's a research lab or a hospital or an industrial manufacturing facility, lasers are used in a variety of applications," says Rao.

Unfortunately, enthusiasm over the utility of lasers seems to have eclipsed concerns about their dangers--and those dangers are considerable. According to the American National Standard for Safe Use of Lasers, even a small-wattage laser can do significant damage when viewed. "A laser pointer operating in the one–to five–milliwatt range can cause injury when its beam--either directly or reflected from a bright surface--hits the eye," Rao explains.

To make matters worse, scenarios like that are becoming all too common as lasers gain wider applicability: "The odds of a laser beam hitting the human eye accidentally are increasing daily," Rao warns.

Rao and his team--currently composed of seven students ranging from undergraduates to postdoctoral researchers--have made it their business to slash those odds. They have developed a system that contains a thin film of azobenzene--an organic material that transmits ordinary and eye-safe laser light but clamps to preset levels any beam that exceeds a certain intensity. The system, which was described in the August 2003 issue of Applied Optics, has been hailed as a photonics breakthrough.

Rao and UMass Boston foresee a number of uses for the device, and a patent application has already been filed. Rao is developing a portable lab model for the U.S. Army Natick Soldier Systems Center, a Massachusetts facility dedicated to improving soldiers' warfighting capabilities. The university's office for Commercial Ventures and Intellectual Property is discussing with several companies the prospect of developing and marketing goggles equipped with the film. "Current goggles completely block the laser beam," says Rao. "The new system allows the beam to be safely viewed"--an obvious advantage for users, like surgeons, who must closely track a beam to its target.

This work with lasers is only one of several projects that have occupied Rao's team of late. The lab has also developed an optical holographic storage device, and a system for computing and information processing that uses nanobioma-terials.

Rao's group is especially excited about its work using Fourier techniques and thin films of the biomaterial bacterior-hodopsin in medical image processing. This research, which has won financial backing from the National Institutes of Health, has been recognized as a significant contribution to fields like breast cancer diagnostics. Says Dr. Carl D'Orsi, professor of radiology and director of the Breast Imaging Center at Atlanta's Emory University, "Outside of pathology, I have never seen anything quite like this [in imaging]."

That's been a typical reaction to Rao's work, but it may soon sound like understatement. If the advances that have come out of the laser lab recently are any indication of what's in store, the field of photonics hasn't seen anything yet.

Image: Professor Gopal Rao (center) of the Physics Department and his team of photonics researchers: (from right to left) postdoctoral research associates Chandra Yelleswarapu and Pengfei Wu, and graduate student Raj Kothapalli. Not pictured: graduate student Louis Barbato and undergraduate students Hennock Legasse, Rhine Hodges, and Cecily Fogarty. (Photo by Harry Brett)

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