Harvard Researchers Control Laser Polarization

Researchers from the Harvard School of Engineering and Applied Sciences have successfully controlled the polarization of semi-conductor lasers, the School announced this month.

The research has a wide variety of practical applications for fields such as satellite communications, quantum cryptography, and biomedical research—all of which demand highly directional lasers.

The researchers—who worked in conjunction with scientists from the Hamamatsu Photonics laboratory Japan—focused on decreasing the beam divergence of semiconductor lasers by affecting the design of the lasers through nanotechnology, rather than employing typically-used polarizers or laser plates.

“We wanted to create integrated optical components for lasers,” said Nanfang Yu, a fifth-year graduate student in engineering who helped lead the project. “Conventionally people use old types of optical components to control polarization...these are very expensive. Our approach is to make microscopic, metallic structures.”

This was the first time that semiconductor lasers have been shown to possess decreased beam divergence as compared to standard semiconductor lasers.

“The idea is that by using nanotechnology we can essentially design a laser beam with certain properties,” said Federico Capasso, an applied physics professor.

Capasso—who led the project along with Yu—called his work “beam engineering.”

“It is a new wave of photonics that we are opening up,” Capasso said.

Though some in industry have expressed great interest in the work—according to Yu—and Harvard has filed a patent on the product, it may be years before the invention will be marketable.

Yu said that researchers are currently working on improving aspects of the prototype with the hope of reaching that goal.

“This is preliminary research,” said Capasso. “Any practical development is years ahead.”

—Staff writer Anita B. Hofschneider at hofschn@fas.harvard.edu.

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