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


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 .

Bill Steele | Cornell News
Further information:

More articles from Power and Electrical Engineering:

nachricht Greater Range and Longer Lifetime
26.10.2016 | Technologie Lizenz-Büro (TLB) der Baden-Württembergischen Hochschulen GmbH

nachricht 3-D-printed magnets
26.10.2016 | Vienna University of Technology

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: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Greater Range and Longer Lifetime

26.10.2016 | Power and Electrical Engineering

VDI presents International Bionic Award of the Schauenburg Foundation

26.10.2016 | Awards Funding

3-D-printed magnets

26.10.2016 | Power and Electrical Engineering

More VideoLinks >>>