DARPA Funds Optical Vortices Research by Prof. Ramachandran and MIT Lincoln Lab

in Faculty, Graduate Student Opportunities, Graduate Students, Grants, News-EP, Recognition, Research, Research-EP
May 18th, 2011

Our ability to manipulate and take advantage of light’s capabilities has already allowed people to do everything from creating the World Wide Web to improving vision. But some new possibilities are on the horizon, including the chance that light may be used to efficiently sort DNA codes or create highly secure communications links impervious to threats and external attacks.

Pictured above is the spiral phase structure of an optical vortex, extracted by interfering it with a conventional light beam.

Pictured above is the spiral phase structure of an optical vortex, extracted by interfering it with a conventional light beam.

As new prospects emerge, Professor Siddharth Ramachandran (ECE) and Dr. Steve Golowich of MIT Lincoln Laboratory are watching closely and in on the latest optics research.

The Defense Advanced Research Project Agency (DARPA) recently awarded $318,784 for a one-year effort to study optical vortices to Ramachandran, the Principal Investigator (PI) on the project, and Golowich. Optical vortices are light beams that possess fundamentally different properties than what we get from lasers and LEDs today.

“Since these beams spin as they propagate in air, there is speculation that they may be more stable and resistant to atmospheric perturbations, similar to what happens when you spin a football while throwing it,” said Ramachandran. “This could have implications for a wide array of scientific disciplines, enabling, for instance, secure quantum communications links for the future, new sorting mechanisms for DNA molecules, or long range sensing.”

It has long been known that light beams possess linear momentum in the direction they’re moving, which is why micro- or nano-particles in their paths can be pushed forward. Scientists are also aware that light can possess angular momentum that allows micro- and nano-particles in the light beam’s path to rotate.

It was only recently, however, that researchers discovered that light could additionally possess orbital angular momentum. These beams, the optical vortices, spin but allow no energy in the center.

Professor Siddharth Ramachandran (ECE)

Professor Siddharth Ramachandran (ECE)

Previously it was thought that optical vortices, while exotic and interesting, have little use because of their inherent instability. But recent work by Ramachandran has shown that novel photonic crystal fiber and related designs can indeed be used to stably manipulate these beams.

Their early findings have led to the current DARPA-funded effort to investigate the properties of these beams in optical fibers and their applicability to creating next generation secure quantum encryption links, by encoding information in different angular momentum states.

Ramachandran’s research group already earned some recognition for their work when Nenad Bozinovic (PhD ’12) won the President’s Award for a presentation on the topic at Boston University’s Science Day on March 23. They also recently published their first results at the 2011 Conference on Lasers and Electro Optics (CLEO) in Baltimore.

-Rachel Harrington (rachelah@bu.edu)