Duke 'all-optical' switch could advance light-based telecommunications

April 28, 2005

DURHAM, N.C. -- Duke University physicists have developed a switching technique that uses a very weak beam of light to control a much stronger beam. The achievement could make optical telecommunications devices perform far more efficiently, and perhaps also aid in the development of futuristic quantum communications devices, the scientists said.

"What's important here is that this is an 'all-optical' switch, using only light, with a weak beam affecting a strong one," said physics professor Daniel Gauthier, the Duke team leader.

Such a switching technique could improve today's telecommunications switching arrays that must repeatedly and inefficiently convert light to electricity and then back to light -- a method especially impractical for very high speed telecommunications networks, Gauthier said in an interview.

Until now, Gauthier said, scientists have primarily demonstrated switching techniques that use stronger light beams to control weaker ones. "And that's not very useful in a telecommunications networking device because you would need a lot of energy to switch a tiny amount," he said.

Gauthier and other team members will describe their findings in the Friday, April 29, 2005, issue of the research journal Science, in a report whose first author is Gauthier's graduate student Andrew Dawes. Additional co-authors are Gauthier's post-doctoral research associate Lucas Illing and former Duke physics undergraduate Susan Clark, who is now in graduate study at Stanford University.

Their research is funded by the Defense Advance Research Projects Agency, the National Science Foundation and the U.S. Army Research Office.

The Duke team's switching system makes use of an instability that Gauthier initially studied in graduate school.

The scientists point two identical beams of laser light at each other while both opposing beams also pass through a warmed rubidium vapor trapped in a glass vacuum tube.

Normally, such counter pointed laser light beams would just unresponsively pass through each other, Gauthier said. But this laser light is of just the right infrared wavelength to be affected by the natural excitations of the rubidium atoms.

This interaction between the light and the rubidium atoms triggers an instability that creates two additional beams. When these secondary beams are projected on a screen, they form an optical pattern. That pattern, consisting of a pair of spots, can be rotated to a new alignment when a third "switching" beam is passed through the rubidium vapor.

Crucially, the strength of the switching beam is also much weaker than the original beams. According to their Science report, the Duke physicists have been able to operate their switch with beams up to 6,500 times weaker than the light in the optical pattern.

"So the idea is, we've got beams that are pointing in one direction and might be going down to a particular place in a network," Gauthier said. "Then, by putting in a very weak beam, we can rotate those original beams to a new orientation. So the spots could then go to different channels in a network system, for example."

The idea of such a weak signal controlling a stronger one "makes the switch 'cascadable,'" Gauthier said. "That's what you need to be able to have the output of one switch affect the input of another switch downstream. No other group we know of has demonstrated this in an all-optical switch."

So far, the Duke group has used weak switching beams consisting of as few as 2,700 individual particles of light, known as photons.

Their report in Science also suggests possible techniques for using switching beams as weak as single photons, perhaps by reducing the size of the laser beams or modifying the atomic vapor.

"There are some applications in quantum information where you would like to have a switch that could be actuated with a single photon," Gauthier said. Quantum computing and telecommunications refers to systems that make use of the quirky features of quantum mechanics to solve otherwise intractable computational problems and provide secure communications channels.

Those quantum effects only manifest themselves in systems where individual photons, electrons or atoms can be manipulated.
Gauthier's laboratory in Duke's Department of Physics is also affiliated with the university's multidisciplinary Fitzpatrick Center for Photonics and Communication Systems, based in the Pratt School of Engineering.

Gauthier is also affiliated with Duke's Center for Nonlinear and Complex Systems. His group's light switching experiment is an example of a nonlinear effect, involving mathematical relationships that are not directly proportional.

Duke University

Related Laser Light Articles from Brightsurf:

Laser technology: New trick for infrared laser pulses
For a long time, scientists have been looking for simple methods to produce infrared laser pulses.

UCF researchers generate attosecond light from industrial laser
University of Central Florida researchers are making the cutting-edge field of attosecond science more accessible to researchers from all disciplines.

Quantum rings in the hold of laser light
Ultracold atoms trapped in appropriately prepared optical traps can arrange themselves in surprisingly complex, hitherto unobserved structures, according to scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences in Cracow.

Making matter out of light: High-power laser simulations point the way
Engineers at UC San Diego developed a set of simulations involving high-power lasers that could help us recreate the transformation of light into matter, and better understand what happened at the very beginning of the universe.

New metasurface laser produces world's first super-chiral light
Researchers have demonstrated the world's first metasurface laser that produces ''super-chiral light'': light with ultra-high angular momentum.

Researchers combine X-rays and laser light to image sprays
Researchers have developed a new laser-based method that provides an unprecedented view of sprays such as the ones used for liquid fuel combustion in vehicle, ship and plane engines.

Laser diode emits deep UV light
Nagoya University researchers say they have designed a laser diode that emits the shortest-wavelength ultraviolet light to-date, with potential applications in disinfection, dermatology, and DNA analyses.

Weaving quantum processors out of laser light
Researchers open a new avenue to quantum computing with a breakthrough experiment: a large-scale quantum processor made entirely of light.

Shedding light on the reaction mechanism of PUVA light therapy for skin diseases
Together with their Munich-based colleagues, a team of physical chemists from Heinrich Heine University Düsseldorf (HHU) has clarified which chemical reactions take place during PUVA therapy.

Laser light detects tumors
A team of researchers from Jena presents a groundbreaking new method for the rapid, gentle and reliable detection of tumors with laser light.

Read More: Laser Light News and Laser Light Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.