Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Chips that can steer light: Record-setting ‘optical phased arrays’ could lead to better laser rangefinders, smaller medical-imaging devices and even holographic TVs

Because of the interference of the phase-shifted light beams emitted by the antennas, images of the MIT logo appear to hover above the surface of the chip.
Image: Jie Sun
Because of the interference of the phase-shifted light beams emitted by the antennas, images of the MIT logo appear to hover above the surface of the chip.

Image: Jie Sun

Abstract:
f you want to create a moving light source, you have a few possibilities. One is to mount a light emitter in some kind of mechanical housing — the approach used in, say, theatrical spotlights, which stagehands swivel and tilt to track performers.

Chips that can steer light: Record-setting ‘optical phased arrays’ could lead to better laser rangefinders, smaller medical-imaging devices and even holographic TVs

Cambridge, MA | Posted on January 11th, 2013

Another possibility, however, is to create an array of light emitters and vary their "phase" — the alignment of the light waves they produce. The out-of-phase light waves interfere with one another, reinforcing each other in some directions but annihilating each other in others. The result is a light source that doesn't move, but can project a beam in any direction.

Such "phased arrays" have been around for more than a century, used most commonly in radar transmitters, which can be as much as 100 feet tall. But in this week's issue of Nature, researchers from MIT's Research Laboratory of Electronics (RLE) describe a 4,096-emitter array that fits on a single silicon chip. Chips that can steer beams of light could enable a wide range of applications, including cheaper, more efficient, and smaller laser rangefinders; medical-imaging devices that can be threaded through tiny blood vessels; and even holographic televisions that emit different information when seen from different viewing angles.

In their Nature paper, the MIT authors — Michael Watts, an associate professor of electrical engineering, Jie Sun, a graduate student in Watts' lab and first author on the paper, Sun's fellow graduate students Erman Timurdogan and Ami Yaacobi, and Ehsan Shah Hosseini, an RLE postdoc — report on two new chips. Both chips take in laser light and re-emit it via tiny antennas etched into the chip surface.

Calculated incoherence

A wave of light can be thought of as a sequence of crests and troughs, just like those of an ocean wave. Laser light is coherent, meaning that the waves composing it are in phase: Their troughs and crests are perfectly aligned. The antennas in the RLE researchers' chips knock that coherent light slightly out of phase, producing interference patterns.

In the 4,096-antenna chip — a 64-by-64 grid of antennas — the phase shifts are precalculated to produce rows of images of the MIT logo. The antennas are not simply turned off and on in a pattern that traces the logo, as the pixels in a black-and-white monitor would be. All of the antennas emit light, and if you were close enough to them (and had infrared vision), you would see a regular array of pinpricks of light. Seen from more than a few millimeters away, however, the interference of the antennas' phase-shifted beams produces a more intricate image.

In the other chip, which has an eight-by-eight grid of antennas, the phase shift produced by the antennas is tunable, so the chip can steer light in arbitrary directions. In both chips, the design of the antenna is the same; in principle, the researchers could have built tuning elements into the antennas of the larger chip. But "there would be too many wires coming off the chip," Watts says. "Four thousand wires is more than Jie wanted to solder up."

Indeed, Watts explains, wiring limitations meant that even the smaller chip is tunable only a row or column at a time. But that's enough to produce some interesting interference patterns that demonstrate that the tuning elements are working. The large chip, too, largely constitutes a proof of principle, Watts says. "It's kind of amazing that this actually worked," he says. "It's really nanometer precision of the phase, and you're talking about a fairly large chip."

Precision engineering

In both chips, laser light is conducted across the chip by silicon ridges known as "waveguides." Drawing light from the optical signal attenuates it, so antennas close to the laser have to draw less light than those farther away. If the calculation of either the attenuation of the signal or the variation in the antennas' design is incorrect, the light emitted by the antennas could vary too much to be useful.

Both chips represent the state of the art in their respective classes. No two-dimensional tunable phased array has previously been built on a chip, and the largest previous non-tunable (or "passive") array had only 16 antennas. Nonetheless, "I think we can go to much, much larger arrays," Watts says. "It's now very believable that we could make a 3-D holographic display."

"I think it's one of the first clearly competitive applications where photonics wins," says Michal Lipson, an associate professor of electrical and computer engineering at Cornell University and head of the Cornell Nanophotonics Group. Within the photonics community, Lipson says, most work is geared toward "the promise that if photonics is embedded in electronic systems, it's going to really improve things. Here, [the MIT team] has developed a complete system. It's not a small component: This system is ready to go. So it's very convincing."

Lipson adds that the tuning limitations of the MIT researchers' prototype chips is no reason to doubt the practicality of the design. "It's just physically hard to come up with a very high number of contacts that are external," she says. "Now, if you were to integrate everything so that it's all on silicon, there shouldn't be any problem to integrate those contacts."

####

For more information, please click here

Contacts:
Sarah McDonnell

617-253-8923

Copyright © Massachusetts Institute of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

MRI, on a molecular scale: Researchers develop system that could one day peer into the atomic structure of individual molecules April 20th, 2014

Iranian Researchers Present New Model to Strengthen Superconductivity at Higher Temperatures April 19th, 2014

Iranian Researchers Produce New Anti-Cancer Drug from Turmeric April 19th, 2014

Innovative strategy to facilitate organ repair April 18th, 2014

Display technology/LEDs/SS Lighting/OLEDs

Transparent Conductive Films and Sensors Are Hot Segments in Printed Electronics: Start-ups in these fields show above-average momentum, while companies working on emissive displays such as OLED are fading, Lux Research says April 17th, 2014

PAM-XIAMEN Offers UV LED wafer April 15th, 2014

Better solar cells, better LED light and vast optical possibilities April 12th, 2014

Printed Electronics Europe - Plastic Logic shows a flexible OLED display for wearable devices April 11th, 2014

Chip Technology

'Exotic' material is like a switch when super thin April 18th, 2014

Scientists open door to better solar cells, superconductors and hard-drives: Research enhances understanding of materials interfaces April 14th, 2014

Obducat has launched a new generation of SINDRE® Nano Imprint production system April 11th, 2014

Scientists in Singapore develop novel ultra-fast electrical circuits using light-generated tunneling currents April 10th, 2014

Optical Computing

Scientists in Singapore develop novel ultra-fast electrical circuits using light-generated tunneling currents April 10th, 2014

Nanosheets and nanowires April 1st, 2014

Unavoidable disorder used to build nanolaser March 25th, 2014

A mathematical equation that explains the behavior of nanofoams March 22nd, 2014

Discoveries

MRI, on a molecular scale: Researchers develop system that could one day peer into the atomic structure of individual molecules April 20th, 2014

Iranian Researchers Present New Model to Strengthen Superconductivity at Higher Temperatures April 19th, 2014

Iranian Researchers Produce New Anti-Cancer Drug from Turmeric April 19th, 2014

'Exotic' material is like a switch when super thin April 18th, 2014

Announcements

MRI, on a molecular scale: Researchers develop system that could one day peer into the atomic structure of individual molecules April 20th, 2014

Iranian Researchers Present New Model to Strengthen Superconductivity at Higher Temperatures April 19th, 2014

Iranian Researchers Produce New Anti-Cancer Drug from Turmeric April 19th, 2014

Innovative strategy to facilitate organ repair April 18th, 2014

Photonics/Optics/Lasers

High-temperature plasmonics eyed for solar, computer innovation April 17th, 2014

Scientists Capture Ultrafast Snapshots of Light-Driven Superconductivity: X-rays reveal how rapidly vanishing 'charge stripes' may be behind laser-induced high-temperature superconductivity April 16th, 2014

Lumerical files a provisional patent that extends the standard eigenmode expansion propagation technique to better address waveguide component design. Lumerical’s EME propagation tool will address a wide set of waveguide applications in silicon photonics and integrated optics April 16th, 2014

Near-field Nanophotonics Workshop in Boston April 14th, 2014

NanoNews-Digest
The latest news from around the world, FREE







  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More














ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE