Featured Research

from universities, journals, and other organizations

Switching One Light Beam With Another, Cornell Provides A Key Component For Photonic Chips

Date:
November 16, 2004
Source:
Cornell University
Summary:
Cornell University researchers have demonstrated for the first time a device that allows one low-powered beam of light to switch another on and off on silicon, a key component for future "photonic" microchips in which light replaces electrons.

Scanning electron microscope photo of a ring resonator coupled to two straight waveguides. By making the resonator either transparent or opaque to a particular wavelength of light, a photonic circuit could control whether or not the light passes from one straight waveguide to the other.
Credit: Image courtesy of Cornell University

ITHACA, N.Y. -- Cornell University researchers have demonstrated for the first time a device that allows one low-powered beam of light to switch another on and off on silicon, a key component for future "photonic" microchips in which light replaces electrons.

Photonics on silicon has been suggested since the 1970s, and previous light-beam switching devices on silicon have been demonstrated, but they were excessively large (by microchip standards) or have required that the beam of light that does the switching be very high-powered. The approach developed by Michal Lipson, Cornell assistant professor of electrical and computer engineering, confines the beam to be switched in a circular resonator, greatly reducing the space required and allowing a very small change in refractive index to shift the material from transparent to opaque.

The advancement of nanoscale fabrication techniques in just the past few years has made it possible to overcome some of the traditional limitations of silicon photonics, Lipson said. Photonic circuits will find their first application in routing devices for fiber-optic communications, she suggests. At present, information that travels at the speed of light through optical fiber must be converted at the end into electrical signals that are processed on conventional electronic chips, then in many cases converted back into optical signals for retransmission, an extremely slow process. The all-optical switch makes it possible to route these signals without conversion.

The all-optical switch is described in the Oct. 28 issue of the journal Nature by Lipson and members of the Cornell Nanophotonics Research Group, which she directs. The researchers used the facilities of the Cornell NanoScale Facility to manufacture the devices on silicon chips. "It is highly desirable to use silicon -- the dominant material in the microelectronic industry -- as the platform for these photonic chips," they said in their paper. The group already has developed other components for silicon photonic chips, including straight and curved waveguides. One of the key components needed, however, is a way for one optical signal to switch another on or off.

Lipson's optical switch is based on a ring resonator, a device already familiar to photonics researchers. When a ring-shaped waveguide is placed tangent to a straight one, photons traveling along the straight waveguide are diverted into the ring and travel around it many times, but only if they match the resonant frequency of the ring, which is determined by its circumference. For the reported experiments, the researchers created a ring 10 micrometers in diameter with a resonance wavelength of 1,555.5 nanometers, in the near infrared.

To turn the switch off, they pumped a second beam of light in the same wavelength range through the system. This light is absorbed by the silicon through a process known as two-photon absorption, creating many free electrons and "holes" (positively charged regions) in the material. This changes the refractive index and shifts the resonant frequency of the ring far enough that it will no longer resonate with the 1,555.5-nanometer signal. The process can theoretically take place in a few tens of picoseconds, the researchers said.

A similar effect can be used in a straight waveguide, but it requires a fairly long distance. Because light travels many times around the ring, the scattering effect is enhanced and the signal can be controlled in a very small space.

For routing applications, Lipson said, a ring resonator coupled to two waveguides could be used. The second waveguide would receive a signal only when the resonator is switched on. She noted that there is very little loss of light in the ring, meaning that light coming into a routing device could be "recycled" and sent on its way with no additional amplification needed.

Ring resonators also could be used as tunable filters, the researchers suggest, for example to separate the many wavelengths of light in multiplexed optical fiber communications systems.

The Nature paper is titled "All-optical switch on silicon: Controlling light with light on chip." Co-authors are Vilson Almeida, a former Cornell graduate student now in the Institute for Advanced Studies in the Technical Center of the Brazilian Air Force ; Carlos Barrios, former Cornell postdoctoral researcher and now a scientist in the Nanophotonics Technology Centre , Universidad Politιnica de Valencia, Spain; and Roberto Panepucci, former Cornell research associate now an assistant professor at Florida International University.

Previous work on nanoscale optical waveguides and photonic coupling is described in a paper, "Overcoming the limitations of microelectronics using Si nanophotonics: solving the coupling, modulation and switching challenges," published in the Institute of Physics journal Nanotechnology , Aug. 2, 2004.

Related Web Sites:

o The Cornell nanophotonics group: http://nanophotonics.ece.cornell.edu/

o Previous Cornell News Service story on photonic microchips: http://www.news.cornell.edu/releases/Feb04/AAAS.Lipson.ws.html


Story Source:

The above story is based on materials provided by Cornell University. Note: Materials may be edited for content and length.


Cite This Page:

Cornell University. "Switching One Light Beam With Another, Cornell Provides A Key Component For Photonic Chips." ScienceDaily. ScienceDaily, 16 November 2004. <www.sciencedaily.com/releases/2004/10/041030184421.htm>.
Cornell University. (2004, November 16). Switching One Light Beam With Another, Cornell Provides A Key Component For Photonic Chips. ScienceDaily. Retrieved April 18, 2014 from www.sciencedaily.com/releases/2004/10/041030184421.htm
Cornell University. "Switching One Light Beam With Another, Cornell Provides A Key Component For Photonic Chips." ScienceDaily. www.sciencedaily.com/releases/2004/10/041030184421.htm (accessed April 18, 2014).

Share This



More Matter & Energy News

Friday, April 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) — After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Horseless Carriage Introduced at NY Auto Show

Horseless Carriage Introduced at NY Auto Show

AP (Apr. 17, 2014) — An electric car that proponents hope will replace horse-drawn carriages in New York City has also been revealed at the auto show. (Apr. 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) — It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
Powered by NewsLook.com
German Researchers Crack Samsung's Fingerprint Scanner

German Researchers Crack Samsung's Fingerprint Scanner

Newsy (Apr. 16, 2014) — German researchers have used a fake fingerprint made from glue to bypass the fingerprint security system on Samsung's new Galaxy S5 smartphone. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins