Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Using a grating with a grade, engineers trap a rainbow

01.07.2008
Lehigh University researchers work at nanoscale to facilitate the integration of optical structures with electrical devices

Engineers working in optical communications bear more than a passing resemblance to dreamers chasing rainbows.

They may not wish literally to capture all the colors of the spectrum, but they do seek to control the rate at which light from across the spectrum moves through optical circuits.

This pursuit is daunting when those circuits contain dimensions measured in nanometers.

At the nanoscale, says Qiaoqiang Gan, a Ph.D. candidate in electrical engineering at Lehigh University in Bethlehem, Pa., engineers hoping to integrate optical structures with electronic chips face a dilemma.

Light waves transmit data with greater speed and control than do electrical signals, which are hindered by the mobility of the electrons in semiconducting materials.

But light is more difficult to control at the nanoscale because of natural limits on its diffraction, or ability to resolve.

"There is a mismatch between nanoelectronics and nanophotonics," says Gan. "Because of the diffraction limit of light, optical circuits are now much larger than their electronic counterparts. This poses an obstacle to the integration of optical structures with electrical devices.

"For that reason, the dream now among photonics researchers is to make optical structures as small as possible and integrate them with electrical devices."

Gan and his colleagues have made a major contribution towards this effort by developing a relatively simple structure that can slow down or even stop light waves over a wide portion of the light spectrum.

On Friday, June 27, they published an article describing their progress in Physical Review Letters (PRL), a publication of the American Physical Society. PRL is one of the most influential international journals devoted to basic physics.

The article, titled "Ultrawide-Bandwidth Slow-Light System Based on THz Plasmonic Graded Metallic Grating Structures," is coauthored by Gan, Zhan Fu, Yujie Ding and Filbert Bartoli. Fu is a Ph.D. candidate in electrical engineering, Ding is a professor of electrical and computer engineering, and Bartoli is professor and department chair of electrical and computer engineering. Bartoli is Gan's adviser, while Ding advises Fu.

The structure developed by his team, says Gan, has the unique ability to arrest the progress of terahertz (THz) light waves at multiple locations on the structure's surface and also at different frequencies.

"Previous researchers have reported the ability to slow down one single wavelength at one narrow bandwidth," says Gan. "We've succeeded in actually stopping THz waves at different positions for different frequencies.

"Our next goal is to develop structures that extend this capability to the near infrared and visible ranges of the spectrum, where optical communications signals are transferred."

The Lehigh researchers report in PRL that their key innovation is a "metallic grating structure with graded depths, whose dispersion curves and cutoff frequencies are different at different locations."

In appearance, this grate resembles the pipes of a pipe organ arranged side by side and decreasing gradually in length from one end of the assembly to the other.

The degree of grade in the metal grate can be "tuned," says Gan, by altering the temperature and modifying the physical features on the surface of the structure.

Likewise, he says, temperature and surface structure can also be adjusted to trigger the release of the light signals after they have been slowed or trapped.

"The separation between the adjacent localized frequencies can be tuned freely by changing the grade of the grating depths," Gan says. "And the propagation characteristics of the trapped surface modes can be controlled by the surface geometry."

By "opening a door to the control of light waves on a chip," says Bartoli, the new Lehigh grating structure could help scientists and engineers reduce the size of optical structures so they can be integrated at the nanoscale with electronic devices.

"Our grating structure can also be scaled to telecommunications frequencies for future possible applications in integrated optical and nano-photonic circuits," he says.

"This might even help us realize such novel applications as a spectrometer integrated on a chip for chemical diagnostics, spectroscopy and signal processing applications."

Gan, who holds an M.S. in electrical engineering from the Chinese Academy of Sciences in Beijing and a B.S. in materials science and engineering from Fudan University in Shanghai, has used computer modeling to develop and test the grating structure. He will begin soon to work with Ding to conduct physical experiments. Ding has made significant progress in generating THz radiation.

It was after reading an article by another researcher in the field that Gan and Fu came up with the idea of developing graded grating structures to trap and slow light waves.

"The other researcher was attempting to use a cylindrical structure to focus light waves into a subwavelength scale for a THz scanning microscope," he says. "We simplified the cylinder to a grating structure and realized that incoming light waves would be trapped at various points across the grade."

Kurt Pfitzer | EurekAlert!
Further information:
http://www.lehigh.edu

More articles from Physics and Astronomy:

nachricht A better way to weigh millions of solitary stars
15.12.2017 | Vanderbilt University

nachricht A chip for environmental and health monitoring
15.12.2017 | Friedrich-Alexander-Universität Erlangen-Nürnberg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>