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Bending Light
A Matter of Science
Bending Light
Novel physics research demonstrates self-bending light

Experimental results generated by Elad Greenfield
Maxwell accelerating beams. Experimental results (a) and theoretical simulation (b) exhibit very good agreement. Both beams bend along an exact circular trajectory reaching 90° bending. Periodic accelerating beams of Maxwell’s equations. (a) Experimental observation of the accelerating periodic beam that bends to 45° while exhibiting about 8 periods of a snake-like trajectory. (b) Simulated beam with the same parameters.
Research from the Faculty of Physics and Solid State Institute, recently published in the leading journal Physical Review Letters, literally sheds new light on an age-old theory. While light is known to travel in a straight line, scientists have asked whether light beams can, without any external intervention, bend themselves along a curved path. The Technion team presents a new family of accelerating beams and periodic accelerating beams which can do just that.

PhD student Ido Kaminer’s research, as part of Distinguished Prof. Moti Segev’s group, provides full solutions to the Maxwell equations - the 19th-century mathematical formulae that describe electromagnetism. “It’s a lot of fun, I believe, to find new physics where it was thought that everything is already known,” says 26-year-old Kaminer, a theoretical physicist who has worked with MSc student Rivka Bekenstein and visiting researcher Yoni Nemirovsky on the theory of this project, and with experimentalist PhD student Elad Greenfield. Kaminer adds that he finds lots of “beautiful physics” to explore in the field of accelerating beams - “an area of research that is accelerating in its own right.”

“When we entered the field about two years ago,” Kaminer explains, “accelerating beams were limited to small angles. Moti posed a question: ‘Using these tools, can we find beams that bend all the way to 90 degrees?’ I have honed special tools from a previous study to create this ‘ultimate’ self-bending beam to achieve such experimental results. Together with Rivka and Yoni, I have developed a technique with which we’ve solved other problems.”

Kaminer accepted his mentor’s challenge and took it to the extreme. “I found something quite illogical,” he says, “I would shine a beam forward and it seemed to go full circle, lighting me from behind as it were.” About one year later, and after taking an advanced course on Einstein’s Theory of Relativity and also observing how light pulses behave in optic fibers, Kaminer felt better equipped to explain his counterintuitive results. “At almost 90 degrees the beam breaks up and the light experiences diffraction broadening. But up to that point, the beam is bending without any diffraction broadening, so we get a new family of non-diffracting beams. What we observed as the full circle was actually the interference of two beams launched from opposite sides, which is interesting in its own right.”

Kaminer presented this breakthrough research at the premier international forum for scientific and technical optics, CLEO (Conference on Lasers and Electro-Optics), in May 2012, and the work has attracted a great deal of attention in the scientific community, securing editorials and commentary in leading publications. The Physical Review Letters paper, which Kaminer and Segev coauthored with Bekenstein and Nemirovsky, was selected as the “Editor’s Suggestion” and for “Viewpoints in Physics.” Several commentary articles have been written about the paper, highlighting its importance, in the prestigious Science and New Scientist magazines.

An important implication of this study is that the underlying concepts are universal, and apply to very many physical systems. The bending of a light beam demonstrated here will occur also for other kinds of wave, such as acoustic and water waves.

Concurrent with this research but independently of it, a group of experimentalists in France led by John Dudley was able to demonstrate the first observation of light self-bending to fairly large angles, using a different method that gave an approximation of the beam found in the Technion. Using the solution found by Kaminer and his coworkers, that team quickly adjusted their launch beam and are now getting close to 90 degrees bending.

“I found something quite illogical…
I would shine a beam forward and it seemed to go full circle, lighting me from behind as it were.”
In parallel, PhD student Elad Greenfield is now manipulating these high-angle bending beams for exciting applications in the biological arena. Interestingly, in principle - giving an initial tilt with a simple prism should allow bending to close to 180 degrees, almost like a boomerang. A perfect boomerang is not really accessible when the beam is launched from a single plane, but getting close to it is feasible.

Zhigang Chen, a physics professor at San Francisco State University, speculated that, “one might expect one day light could really travel around a circle by itself, bringing the search for an ‘optical boomerang’ into reality.”

Applications of these ideas could include particle manipulations using the curved light; burning curved holes through materials; plasmonic surface waves with improved range; and atmospheric spectroscopy to detect chemical/biological agents.

As an undergraduate, Kaminer participated in the premier Technion programs for undergraduate students: the Technion’s Excellence Program and the elite pre-military service Psagot Program (Physics-Electrical Engineering Dual Degree Program).

Distinguished Prof. Mordechai (Moti) Segev holds the Norman and Trudy Louis Chair in Engineering
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