My specialty is in laser material processing. In a word, I use lasers to treat various materials and see their behavior.

Assistant Professor of Mechanical Engineering Sinisa Vukelic is a blacksmith for the 21st century. Rather than use iron and a hammer, he works with aluminum and lasers, but he is still concerned with strengthening metals by striking them with a sharp blow. The technique of hardening metal with lasers has been used on a large scale to manufacture military jet engines for some time. Vukelic studies the fundamental properties of how the same process works on a microscopic scale. Such understanding could find an application in the manufacture of microswitches, which are used to control electrical circuits in everything from computer mice to fire sprinkler systems.

Any piece of metal bent back and forth repeatedly will eventually break. Shocking the metal with a laser pulse, delivered in a confining medium such as water, creates a tremendous pressure, which closes up tiny cracks in the metal and should make it more durable.

"What I'm trying to do is treat the specimen such that it can last longer before it breaks," says Vukelic.

His research is focused on single and bi-crystals of aluminum, which allows him to concentrate on illuminating fundamental physical properties in the absence of the variability that naturally occurs between different crystals.

Laser deformation is only one aspect of Vukelic's broader research program. "My specialty is in laser material processing," he says. "In a word I use lasers to treat various materials and see their behavior."

Vukelic also studies femtosecond lasers, which produce extremely fast pulses, only a few hundred femtoseconds, or 10-15 seconds, in duration. These specialized lasers were invented in the 1980s, and have gained attention as their reliability increased over the past 15 years. The ultrafast pulses from femtosecond lasers give them unique capabilities. For instance, the laser can be pinpointed to one specific point within a material.

"You can process the interior of a transparent material such as glass without affecting its surface," Vukelic says. One angle of this research is focused on microexplosions. "I focus the laser inside of the glass, and each pulse creates a small cavity inside of the glass surrounded by the densified shell," he says "This has potential usage in 3-D optical data storage."

Repeated pulses from the femtosecond laser can also cause thermal accumulation to occur. This phenomenon has potential application in the development of optical waveguides, which are used to transfer information in the form of pulses of light.

While Vukelic's research has diverse potential applications, his foremost interest is in understanding the fundamental physics underlying the response of materials to laser treatments.

Posted Sept. 22, 2009

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