Antenna design turns entire vehicles into broadcasting equipment

High-frequency antennas transmit radio waves across vast distances and even over mountain ranges using very little energy, making them ideal for military communications. These devices, however, have one big problem: They need to be huge to operate efficiently.

Instead of adding more bulk, University of Wisconsin–Madison engineers are working to increase the effective size of antennas by turning the military vehicles that carry them into transmitters — using the structures that support the antennas themselves to help broadcast signals.

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Scientists demonstrate highly directional semiconductor lasers

CAMBRIDGE, Mass. – July 28, 2008 – Applied scientists at Harvard University in collaboration with researchers from Hamamatsu Photonics in Hamamatsu City, Japan, have demonstrated, for the first time, highly directional semiconductor lasers with a much smaller beam divergence than conventional ones. The innovation opens the door to a wide range of applications in photonics and communications. Harvard University has also filed a broad patent on the invention.

Spearheaded by graduate student Nanfang Yu and Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, all of Harvard's School of Engineering and Applied Sciences (SEAS), and by a team at Hamamatsu Photonics headed by Dr. Hirofumi Kan, General Manager of the Laser Group, the findings were published online in the July 28th issue of Nature Photonics and will appear in the September print issue.

"Our innovation is applicable to edge-emitting as well as surface-emitting semiconductor lasers operating at any wavelength—all the way from visible to telecom ones and beyond," said Capasso. "It is an important first step towards beam engineering of lasers with unprecedented flexibility, tailored for specific applications. In the future, we envision being able to achieve total control of the spatial emission pattern of semiconductor lasers such as a fully collimated beam, small divergence beams in multiple directions, and beams that can be steered over a wide angle."

While semiconductor lasers are widely used in everyday products such as communication devices, optical recording technologies, and laser printers, they suffer from poor directionality. Divergent beams from semiconductor lasers are focused or collimated with lenses that typically require meticulous optical alignment—and in some cases bulky optics.

To get around such conventional limitations, the researchers sculpted a metallic structure, dubbed a plasmonic collimator, consisting of an aperture and a periodic pattern of sub-wavelength grooves, directly on the facet of a quantum cascade laser emitting at a wavelength of ten microns, in the invisible part of the spectrum known as the mid-infrared where the atmosphere is transparent. In so doing, the team was able to dramatically reduce the divergence angle of the beam emerging from the laser from a factor of twenty-five down to just a few degrees in the vertical direction. The laser maintained a high output optical power and could be used for long range chemical sensing in the atmosphere, including homeland security and environmental monitoring, without requiring bulky collimating optics.

"Such an advance could also lead to a wide range of applications at the shorter wavelengths used for optical communications. A very narrow angular spread of the laser beam can greatly reduce the complexity and cost of optical systems by eliminating the need for the lenses to couple light into optical fibers and waveguides," said Dr. Kan.

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New Technique Stores and Retrieves Entire Image from a Single Photon

Ultra-Dense Optical Storage — on One Photon

Researchers at the University of Rochester have made an optics breakthrough that allows them to encode an entire image's worth of data into a photon, slow the image down for storage, and then retrieve the image intact.

While the initial test image consists of only a few hundred pixels, a tremendous amount of information can be stored with the new technique.

The image, a "UR" for the University of Rochester, was made using a single pulse of light and the team can fit as many as a hundred of these pulses at once into a tiny, four-inch cell. Squeezing that much information into so small a space and retrieving it intact opens the door to optical buffering—storing information as light.

"It sort of sounds impossible, but instead of storing just ones and zeros, we're storing an entire image," says John Howell, assistant professor of physics and leader of the team that created the device, which is revealed in today's online issue of the journal Physical Review Letters. "It's analogous to the difference between snapping a picture with a single pixel and doing it with a camera—this is like a 6-megapixel camera."

"You can have a tremendous amount of information in a pulse of light, but normally if you try to buffer it, you can lose much of that information," says Ryan Camacho, Howell's graduate student and lead author on the article. "We're showing it's possible to pull out an enormous amount of information with an extremely high signal-to-noise ratio even with very low light levels."

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First Demonstration of a Working Invisibility Cloak

The cloak, made with advanced 'metamaterials,' deflects microwave beams and may find a variety of wireless communications or radar applications

Thursday, October 19, 2006

Durham, NC -- A team led by scientists at Duke University's Pratt School of Engineering has demonstrated the first working "invisibility cloak." The cloak deflects microwave beams so they flow around a "hidden" object inside with little distortion, making it appear almost as if nothing were there at all.

Cloaks that render objects essentially invisible to microwaves could have a variety of wireless communications or radar applications, according to the researchers.

The team reported its findings on Thursday, Oct. 19, in Science Express, the advance online publication of the journal Science. The research was funded by the Intelligence Community Postdoctoral Fellowship
The researchers manufactured the cloak using "metamaterials" precisely arranged in a series of concentric circles that confer specific electromagnetic properties. Metamaterials are artificial composites that can be made to interact with electromagnetic waves in ways that natural materials cannot reproduce.

The cloak represents "one of the most elaborate metamaterial structures yet designed and produced," the scientists said. It also represents the most comprehensive approach to invisibility yet realized, with the potential to hide objects of any size or material property, they added.

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State hopes to blanket cities with wireless Internet access

State hopes to blanket cities with wireless Internet access

(Published Thursday, January 19, 2006 07:29:41 AM CST)

By Dinesh Ramde
Associated Press

MILWAUKEE - When she needs to surf the Internet away from school, Jennifer Roeh's only option is to stop by a local coffee shop.

. . .

Matt Miszewski, Wisconsin's chief information officer, said making Wi-Fi access a priority would build the state's reputation for technology savvy.

"We want businesspeople to know they can land at the airport and have connectivity from the airport all the way to their hotel rooms," he said.

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New Rules On Internet Wiretapping Challenged

New Rules On Internet Wiretapping Challenged
Redesign Costs Are Cited

By Arshad Mohammed
Washington Post Staff Writer
Wednesday, October 26, 2005; Page D01

New federal wiretapping rules that would make it easier for law enforcement to monitor e-mails and Internet-based phone calls were challenged by privacy, high-tech and telecommunications groups in federal court yesterday.

The groups argued that the rules would force broadband Internet service providers, including universities and libraries, to pay for redesigning their networks to make them more accessible to court-ordered wiretaps.

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Congress Tunes In to WiFi

Congress Tunes In to WiFi

By Robert MacMillan Staff Writer
Monday, June 27, 2005; 10:45 AM

Mick Jagger said it best: 'The summer's here and the time is right for fighting in the street, boy."

The streets run through U.S. cities and towns, where the heat is on local governments to provide free or low-cost Internet access.

For almost a year, the debate over whether Internet access is a paid privilege like telephone service and cable television burbled along in the press and among bloggers and activists. Many see it as necessary to attract new residents, tourists and businesses. Internet service providers, however, see a threat to their billion-dollar high-speed access business. Now that cities such as Philadelphia are trying to make it a reality, the issue's significance is cresting. There's no better way to prove that than with two sets of numbers: 1294 and 2726.

The first is a Senate bill introduced last Thursday by Sens. John McCain (R-Ariz.) and Frank Lautenberg (D-N.J.). The Community Broadband Act of 2005 says "no state can prohibit a municipality from offering broadband to its citizens."

The second is a bill introduced in late May in the House by Rep. Pete Sessions (R-Texas). The Preserving Innovation in Telecom Act of 2005 -- almost surely destined for shorthand treatment as "PRITA" -- says state and local governments can't offer Internet service if a private provider already does.

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New UW lab to study RFID

New UW lab to study RFID

By Lynn Welch
June 23, 2005

Madison has become home to a new laboratory to study radio frequency identification technology, or RFID.

The University of Wisconsin-Madison's E-Business Consortium late last year established its RFID lab to put into practice concepts studied by the group's RFID workgroup. During the first half of this year, the lab has been installing donated equipment and preparing for an official opening Aug. 12, announced Wednesday during the consortium's second annual RFID Conference in Waukesha.

"There was a need for ways to validate the practicality of the benefits of this technology," said lab director and consortium associate director of research and education Alfonso Gutierrez. "There was also a need to service an educational avenue where companies could have a safe place to come without having to be under pressure."

Taking the consortium's charge of providing Wisconsin firms a technology sandbox where corporate issues can be explored in an unbiased academic setting, the RFID lab was created with donated equipment form Rockwell Automation, Autologik, RedPrairie and Dorner Manufacturing.

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NIST Photon Detectors Have Record Efficiency

NIST Photon Detectors Have Record Efficiency

The four yellow squares in the center of this micrograph are NIST single photon detectors. The top two detectors are 25 by 25 micrometers. The bottom two detectors are 50 by 50 micrometers. The detectors operate with a record 88 percent efficiency.

Sensors that detect and count single photons, the smallest quantities of light, with 88 percent efficiency have been demonstrated by physicists at the National Institute of Standard and Technology (NIST). This record efficiency is an important step toward making reliable single photon detectors for use in practical quantum cryptography systems, the most secure method known for ensuring the privacy of a communications channel.

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