Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cornell-developed tools to guide and switch light could lead to photonic microchips and practical home fiber-optic lines

16.02.2004


A Cornell University researcher is developing techniques for making photonic microchips -- in which streams of electrons are replaced by beams of light -- including ways to guide and bend light in air or a vacuum, to switch a beam of light on and off and to connect nanophotonic chips to optical fiber.



Michal Lipson, an assistant professor at Cornell, in Ithaca, N.Y., described recent research by the Nanophotonics Group in Cornell’s School of Electrical and Computer Engineering at the annual meeting of the American Association for the Advancement of Science (AAAS) in Seattle on Sunday, Feb. 15. Her talk was part of a symposium on "21st Century Photonics."

Lipson suggested that one of the first applications of nanophotonic circuits might be as routers and repeaters for fiber-optic communication systems. Such technology, she added, could speed the day when home use of fiber-optic lines becomes practical.


Researchers already have built nanoscale photonic devices in which wires are replaced by square waveguides that confine light by total internal reflection. This works only in materials with a high index of refraction, such as silicon, where there is a loss of light intensity and sometimes distortion of pulses. Lipson described a way to guide and bend light in low-index materials, including air or a vacuum. "In addition to reducing losses, this opens the door to using a wide variety of low-index materials, including polymers, which have interesting optical properties," Lipson said.

Using equipment at the National Science Foundation-supported Cornell Nanoscale Facility, Lipson’s group has manufactured waveguides consisting of two parallel strips of a material with a high refractive index placed about 50 to 200 nanometers apart, with a slot containing a material of much lower refractive index. (A nanometer is about the width of three silicon atoms.) In some

devices the walls are made of silicon with an air gap, and others have silicon dioxide walls with a silicon gap. In both cases, the index of refraction of the medium in the gap is much lower than that of the wall, up to a ratio of about four to one.



When a wavefront crosses two materials of very different refractive indices and the low-index space is very narrow in proportion to the wavelength, nearly all of the light is confined in the "slot waveguide." Theory predicts that straight slots will have virtually no loss of light, and smooth curves will have only a small loss. This has been verified by experiments, Lipson reported.

Slot waveguides can be used to make ring resonators, already familiar to nanophotonics researchers. When a circular waveguide is placed very close to a straight one, some of the light can jump from the straight to the circular waveguide, depending on its wavelength. "In this way we can choose the wavelength we want to transmit," Lipson said. In fiber-optic communications, signals often are multiplexed, with several different wavelengths traveling together in the same fiber, each wavelength carrying a different signal. Ring resonators can be used as filters to separate these signals, she suggested.

Like the transistor switches in conventional electronic chips, light-beam switches would be the basic components of photonic computers. Lipson’s group has made switches in which light is passed in a straight line through a cavity with reflectors at each end, causing the light to bounce back and forth many times before passing through. The refractive index of the cavity is varied by applying an electric field; because of the repeated reflections, the light remains in the waveguide long enough to be affected by this small change. Lipson is working on devices in which the same effect is induced directly by another beam of light.

Connecting photonic chips to optical fibers can be a challenge because the typical fiber is vastly larger than the waveguide. It’s like connecting a garden hose to a hypodermic needle. Most researchers have used waveguides that taper from large to small, but the tapers typically have to be very long and introduce losses. Instead, Lipson’s group has made waveguides that narrow almost to a point. When light passes through the point, the waveform is deformed as if it were passing through a lens, spreading out to match the larger fiber. Conversely, the "lens" collects light from the fiber and focuses it into the waveguide. Lipson calls this coupling device "optical solder." Based on experiments at Cornell, the device could couple 200-nanometer waveguides to 5-micron fibers with 95 per cent efficiency, she reported. It can also be used to couple waveguides of different dimensions.

The method of coupling nanoscale waveguides to optical fiber is described in a paper, "Nano-taper for Compact Mode Conversion," published in Optics Letters ( August 2003). Slot waveguides are described in "Guiding and Confining Light in Void Nanostructures," accepted for publication in Optics Letters . Some of the work has been done in collaboration with researchers working under Alexander Gaeta, Cornell associate professor of applied and engineering physics. The Cornell nanophotonics group web site is http://nanophotonics.ece.cornell.edu/ .

Bill Steele | Cornell News
Further information:
http://www.news.cornell.edu/releases/Feb04/AAAS.Lipson.ws.html
http://nanophotonics.ece.cornell.edu/

More articles from Power and Electrical Engineering:

nachricht Engineer Improves Rechargeable Batteries with MoS2 Nano 'Sandwich'
17.04.2015 | Kansas State University

nachricht Packing Heat: New Fluid Makes Untapped Geothermal Energy Cleaner
17.04.2015 | Pacific Northwest National Laboratory

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Astronomers reveal supermassive black hole's intense magnetic field

Astronomers from Chalmers University of Technology have used the giant telescope Alma to reveal an extremely powerful magnetic field very close to a supermassive black hole in a distant galaxy

Astronomers from Chalmers University of Technology have used the giant telescope Alma to reveal an extremely powerful magnetic field very close to a...

Im Focus: A “pin ball machine” for atoms and photons

A team of physicists from MPQ, Caltech, and ICFO proposes the combination of nano-photonics with ultracold atoms for simulating quantum many-body systems and creating new states of matter.

Ultracold atoms in the so-called optical lattices, that are generated by crosswise superposition of laser beams, have been proven to be one of the most...

Im Focus: UV light robot to clean hospital rooms could help stop spread of 'superbugs'

Can a robot clean a hospital room just as well as a person?

According to new research out of the Texas A&M Health Science Center College of Medicine, that is indeed the case. Chetan Jinadatha, M.D., M.P.H., assistant...

Im Focus: Graphene pushes the speed limit of light-to-electricity conversion

Researchers from ICFO, MIT and UC Riverside have been able to develop a graphene-based photodetector capable of converting absorbed light into an electrical voltage at ultrafast timescales

The efficient conversion of light into electricity plays a crucial role in many technologies, ranging from cameras to solar cells.

Im Focus: Study shows novel pattern of electrical charge movement through DNA

Electrical charges not only move through wires, they also travel along lengths of DNA, the molecule of life. The property is known as charge transport.

In a new study appearing in the journal Nature Chemistry, authors, Limin Xiang, Julio Palma, Christopher Bruot and others at Arizona State University's...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

HHL's Entrepreneurship Conference on FinTech

13.04.2015 | Event News

World Conference On Regenerative Medicine 2015: Registration And Abstract Submission Now Open

25.03.2015 | Event News

University presidents from all over the world meet in Hamburg

19.03.2015 | Event News

 
Latest News

Engineer Improves Rechargeable Batteries with MoS2 Nano 'Sandwich'

17.04.2015 | Power and Electrical Engineering

Comparing Climate Models to Real World Shows Differences in Precipitation Intensity

17.04.2015 | Earth Sciences

A blueprint for clearing the skies of space debris

17.04.2015 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>