Category Archives: Future
Posted February 17, 2013 – 05:00 by Randy Woods, EarthTechling
There are some fanciful architectural designs that look wonderful, almost dreamlike, in drawings, but you know will almost never get built in the real world.
One design from Italian architect Stefano Boeri, however, appears to be turning that notion on its head with his Bosco Verticale, or “Vertical Forest,” which is growing like a mighty oak in the smoggy city of Milan, Italy.
An article on the project in Jetson Green described Milan as one of the most polluted cities in Europe, with some of the worst air quality in the European Union. It’s only fitting, then, that Boeri’s design of two residential towers that will be plastered with oxygen-spewing trees and other plants was greenlighted a few years ago, if only to help clear the city’s air.
This structure of these 365-foot and 256-foot towers is nearly complete and should be ready to open later this year. The vertical forest aspect is beginning to take shape as crews are starting to hoist the first of the 900 trees, 5,000 shrubs and 11,000 smaller plants that will be planted in terraces that cover nearly every vertical façade of each tower.
The trees will take root in deep concrete planters that are situated in the nearly 97,000 square feet of terrace space around both towers. Irrigation will be partially provided by the collection and reuse of greywater on the site. Renewable energy also will be supplied through passive and photovoltaic solar methods.
Each resident of the towers will have a view of the city through the lush greenery, which will create its own microclimate that can add a number of benefits to daily life besides just aesthetic value. For instance, the plants will help mitigate smog by consuming CO2 and producing oxygen, while also providing new habitat for insects and birds. When the summer temperatures of Milan begin rising past 100 degrees Fahrenheit, the plants will provide shade and help cool the apartments to reduce energy costs. During stormy days, the well-rooted trees will act as a windbreak and will also help muffle the sounds of the streets below.
According to Boeri’s site, the verticality of the project provides both housing and urban forest space in a very compact area. The amount of greenery on the two buildings, he said, will equal an area or more than 107,000 square feet of natural forest land and about 538,000 square feet of living space—all in the space of a city block.
The Bosco Verticale project is part of a larger rehabilitation plan for the historic district between Via De Island Castillia and Confalonieri. According to Jetson Green, Boeri’s design has inspired other vertical forest ideas, including a social housing tower in Spain, called the Torre Huerta, and a “Flower Tower” in Paris, featuring nearly 400 bamboo plants.
By Mat Smith
The high-definition pride of your living room may not want to hear it, but it looks like ultra high-definition TV (or UHDTV) has now taken another step towards reality. While shop-floor products remain years away, experts in the ITU Study Group on Broadcasting Service have made several agreements on technical standards for your (next?) next TV purchase. Increasing pixel count in future sets is also expected to improve viewing angles on glasses-free 3D, which needs more dots to work its lenticular magic. 33 megapixels sounds like it should be enough to work with.
By Darren Quick
Graphene has already brought us the world’s smallest transistor – twice – and now the one atom thick form of carbon that recently won its discoverers the Nobel Prize has been used to create a triple-mode, single-transistor amplifier. The new transistor has the potential to replace many traditional transistors in a typical integrated circuit and its developers say the device could become a key component in future electronic circuits.
Aside from being very strong, nearly transparent and being a very good conductor of electricity, graphene is also ambipolar, meaning it is able to switch between using positive and negative carriers on the fly depending on the input signal. In comparison, traditional silicon transistors usually only use one or the other type of carrier, which is determined during fabrication. It is graphene’s ambipolar property that has allowed the researchers from Rice University and the University of California, Riverside, to develop the new three-terminal single-transistor amplifier.
The triple-mode transistor can be changed during operation to any of three modes at any time using carriers that are positive, negative or both. This provides opportunities that are not possible with traditional single-transistor architectures, said Kartik Mohanram, an assistant professor of electrical and computer engineering at Rice.
Mohanram likened the new transistor”s abilities to that of a water tap. “Turn it on and the water flows,” he said. “Turn it off and the water stops. That”s what a traditional transistor does. It”s a unipolar device – it only opens and closes in one direction. But if you close a tap too much, it opens again and water flows. That”s what ambipolarity is – current can flow when you open the transistor in either direction about a point of minimum conduction.”
This means a graphene-based transistor can be “n-type” (negative) or “p-type” (positive), depending on whether the carrier originates from the source or drain terminals, which are effectively interchangeable. When the input from each carrier is equal, a third function appears with the transistor becoming a frequency multiplier. By combining the three modes, the Rice-Riverside team demonstrated such common signaling schemes as phase and frequency shift keying for wireless and audio applications.
“Our work, and that of others, that focuses on the applications of ambipolarity complements efforts to make a better transistor with graphene,” Mohanram said. “It promises more functionality.” The research demonstrated that a single graphene transistor could potentially replace many in a typical integrated circuit, he said. Graphene”s superior material properties and relative compatibility with silicon-based manufacturing should allow for integration of such circuits in the future, he added.
However, technical roadblocks still need to be overcome before that happens. Fabrication steps such as dielectric deposition and making contacts actually disturb graphene’s lattice structure, scratching it and introducing defects, which immediately limits its signal gain and degrades its performance. This means the team has to exercise a lot of care when making the transistors.
But Mohanram is confident these problems can be overcome, saying, “the technology will mature, since so many research groups are working hard to address these challenges.”
A paper detailing the triple-mode transistor appears in the online journal ACS Nano.
By Brian Nade
Tired of the stale cookie-cutter designs that make all laptops look basically alike? You’re not alone. A group of intrepid designers and engineers is doing something about the “sameness syndrome” that permeates notebook design. They’re working on groundbreaking concept designs that not only turn heads but also point to new ways to work and play on the road.
Just as car shows give us a sneak peek into the next big thing in automotive technology, concept and prototype designs provide a crystal ball to see what tomorrow might have in store for mobility.
“Design concepts allow us to stretch our imaginations and ask ‘what if,’ ” says Murali Veeramoney, head of the concept PC program at Intel‘s Santa Clara, Calif., headquarters. “They help us see the future of computing.”
Get ready for a revolution in notebook design, including laptops with multiple screens or slide-out keyboards as well as computers that can be folded into different shapes or even rolled up when not in use. How about a laptop that can be charged without being plugged in? Even the definition of “laptop” is changing, with lines blurring among traditional notebooks, netbooks, convertible tablets, iPad-style slate tablets, smartbooks, e-readers, ultramobile PCs and other mobile Internet devices.
A couple of years back, I took a look at what kind of notebooks we might be using in the year 2015, but they required a technological breakthrough or two to become reality. In contrast, the 12 innovative notebook designs here — some actual working computers, others wooden mockups or CAD drawings — are for the most part producible within the next two years.
“Folding screens, wireless charging, rollup computers — it’s all coming in the next couple of years,” says Leslie Fiering, a research vice president at Gartner. “Designers are getting more and more creative and innovative.”
Here’s a peek at the not-so-distant future.
Four screens, no waiting
What if your next notebook had two, three or even four displays, each capable of making your computing experience more enjoyable and efficient? That’s the idea behind the Tangent Bay laptop created by Veeramoney’s notebook prototype group at Intel.
A full working computer that shows the possibility of fresh thinking on screens, the Tangent Bay has a prominent 15.6-in. main display along with three auxiliary 3.5-in. OLED touch screens, which are usually used on cell phones.
Evenly spaced just above the keyboard, these auxiliary displays can be dedicated to specific tasks so that the main screen doesn’t get crowded with a plethora of panes and menus.
They’re good for anything from showing a reminder note or running a live RSS feed to displaying a clock or Photoshop’s brush menu. With a little programming, Veeramoney says, you could even stash your Windows 7 Gadgets there. Personally, I would use the smaller screens to monitor my e-mail and favorite Web sites without cluttering up the main screen.
“Call it extreme multitasking, but people have multiple things going on,” explains Veeramoney. “If you want to bring any of them to the main screen, just flick it upwards with your finger. Touch is a very exciting concept for us.”
When the Tangent Bay was introduced at last year’s Intel Developer Forum in San Francisco (see video), the response was enormous. People immediately got it and saw that the multiple screens can keep several snippets of information front and center without overwhelming the user.
With an ultra-low-voltage processor inside, Tangent Bay is about as thick as a current mainstream business notebook, but slightly heavier due to the extra displays. The best part is that this system requires no new technology or engineering advances and could be made today.
“The goal of our work is commercialization,” adds Veeramoney, although commercial restrictions prevent him from talking about any plans Intel might have to bring this technology to market.
Often, these prototypes are looked over by several notebook manufacturers, which take pieces and ideas and incorporate them into their wares. Tangent Bay probably won’t see the light of day as a single model, but it will likely live on in several future notebooks from multiple makers.
Prime: Although it was designed as the ultimate gaming machine with two processors and a high-end graphics engine, the Prime laptop folds up to the size of a 13-in. notebook. Unfold it and it can be a huge tablet workspace, a clamshell notebook with a 26-in. ultrawide screen or one with a traditional 15-in. 4:3 ratio display. It’s composed of six aluminum wings that slide and hinge to create several different configurations, each suited to a different style of work or play.
On a bender: This machine is testing the electrical properties of a graphene sheet. Korean researchers have incorporated these stretchy electrodes with thin-film nano-generators to make an energy-harvesting screen. Credit: Advanced Materials
Touch-responsive nano-generator films could power touch screens.
Touch-screen computing is all the rage, appearing in countless smart phones, laptops, and tablet computers.
Now researchers at Samsung and Sungkyunkwan University in Korea have come up with a way to capture power when a touch screen flexes under a user’s touch. The researchers have integrated flexible, transparent electrodes with an energy-scavenging material to make a film that could provide supplementary power for portable electronics. The film can be printed over large areas using roll-to-roll processes, but are at least five years from the market.
The screens take advantage of the piezoelectric effect–the tendency of some materials to generate an electrical potential when they’re mechanically stressed. Materials scientists are developing devices that use nanoscale piezoelectronics to scavenge mechanical energy, such as the vibrations caused by footsteps. But the field is young, and some major challenges remain. The power output of a single piezoelectric nanowire is quite small (around a picowatt), so harvesting significant power requires integrating many wires into a large array; materials scientists are still experimenting with how to engineer these screens to make larger devices.
Samsung’s experimental device sandwiches piezoelectric nanorods between highly conductive graphene electrodes on top of flexible plastic sheets. The group’s aim is to replace the rigid and power-consuming electrodes and sensors used on the front of today’s touch-screen displays with a flexible touch-sensor system that powers itself. Ultimately, this setup might generate enough power to help run the display and other parts of the device functions. Rolling up such a screen, for instance, could help recharge its batteries.
“The flexibility and rollability of the nano-generators gives us unique application areas such as wireless power sources for future foldable, stretchable, and wearable electronics systems,” says Sang-Woo Kim, professor of materials science and engineering at Sungkyunkwan University. Kim led the research with Jae-Young Choi, a researcher at Samsung Advanced Institute of Technology.
The same group previously put nano-generators on indium tin oxide electrodes. This transparent, conductive material is used to make the electrodes on today’s displays, but it is inflexible.
To make the new nano-generators, the researchers start by growing graphene–a single-atom-thick carbon material that’s highly conductive, transparent, and stretchy–on top of a silicon substrate, using chemical vapor deposition. Next, through an etching process developed by the group last year, the graphene is released from the silicon; and the graphene is removed by rolling a sheet of plastic over the surface. The graphene-plastic substrate is then submerged in a chemical bath containing a zinc reactant and heated, causing a dense lawn of zinc-oxide nanorods to grow on its surface. Finally, the device is topped off with another sheet of graphene on plastic.
In a paper published this month in the journal Advanced Materials, the Samsung researchers describe several small prototype devices made this way. Pressing the screen induces a local change in electrical potential across the nanowires that can be used to sense the location of, for example, a finger, as in a conventional touch screen. The material can generate about 20 nanowatts per square centimeter. Kim says the group has subsequently made more powerful devices about 200 centimeters squared. These produce about a microwatt per square centimeter. Kim says this is enough for a self-powered touch sensor and “indicates we can realize self-powered flexible portable devices without any help of additional power sources such as batteries in the near future.”
“It’s pretty impressive to integrate all these things in a foldable, macroscale device,” says Michael McAlpine, professor of mechanical engineering at Princeton University. He notes that the potential of zinc oxide nanowires as a piezoelectric sensing material and nanoscale power source was previously demonstrated by Georgia Tech materials scientist Zhong Lin Wang. But integrating these materials over a large area with a flexible, transparent electrode opens up new applications, says McAlpine.
The methods used to make the nano-generators are compatible with large-scale manufacturing, according to Kim. His group is working to boost the power output of the films–the main obstacle is the quality of the electrodes. One possible solution is to improve the connection between the nanowires and the electrodes by eliminating flaws in the structure of the graphene. The Korean group is also experimenting with adding small amounts of impurities to the material, a process called doping, to improve its conductivity.
The new generation of e-book reading gadgets will transform the troubled book, magazine, and newspaper industries. But it’s uncertain what that transformation will look like.
By Wade Roush
For serious readers, products like Amazon’s Kindle 2, Barnes and Noble’s Nook, and Sony’s Daily Edition are a godsend. It’s not just that these electronic reading devices are handy portals to hundreds of thousands of trade books, textbooks, public-domain works, and best-sellers, all of which can be wirelessly downloaded at a moment’s notice, and to scores of magazines and newspapers, which show up on subscribers’ devices automatically. They’re also giving adventurous authors and publishers new ways to organize and market their creations. A California startup called Vook, for example, has begun to package cookbooks, workout manuals, and even novels with illustrative video clips, and it’s selling these hybrids of video and text to iPhone, iPad, and iPod Touch owners through Apple’s iTunes Store.
Unfortunately, you can’t get away with charging hardcover prices for an e-book, which makes it hard to see how traditional publishers will profit in a future that’s largely digital. As a result, book publishers are facing a painful and tumultuous time as they attempt to adapt to the emerging e-book technologies. The Kindle, the iPad, and their ilk will force upon print-centric publishers what the Internet, file sharing, and the iPod forced upon the CD-centric music conglomerates starting around 1999–namely, waves of cost cutting and a search for new business models.
Publishers are lucky in one way: the reckoning could have come much sooner. From 1999 to 2001, I worked for NuvoMedia, a Silicon Valley startup that developed a device called the Rocket eBook. The Rocket and its main rival at the time, the Softbook Reader from Softbook Press, prefigured the current generation of e-book devices. Owners could shop for books from major publishers online, download the publications to their PCs, and then transfer them to the portable devices, which had monochrome LCD screens that showed one page of text at a time.
But three factors conspired to kill these first-generation e-readers. First, book publishers, fearing that digital sales would cannibalize print sales, offered only a limited catalogue of books in electronic form and charged nearly as much for Rocket and Softbook editions as they did for hardcovers. Not surprisingly, consumers demurred, which in turn discouraged publishers from offering more titles digitally. Second, the technology wasn’t quite ready for mass adoption. The devices weren’t small or thin enough to be truly portable, and the book-buying process was convoluted. Third, NuvoMedia and Softbook Press were acquired and then combined by a larger company, Gemstar, that was distracted by other issues and let its new e-book division languish, eventually closing it down.
Business conditions are very different today. For one thing, there are more big players with an interest in seeing the e-book business blossom, including Sony, Amazon, Barnes and Noble, and now Apple. Using their pull with publishers, these companies have assembled huge catalogues of e-books–Amazon has nearly half a million commercial titles–and they’ve kept prices lower, in the $10-to-$15 range for new trade books.
Just as important, mobile computing technology has improved drastically. Cheap 3G data access is the biggest advance. Now that readers can browse, purchase, and download e-books and periodicals directly on their devices, they can access new material almost instantaneously, without having to be near a desktop or laptop computer with an Internet connection. Having owned a Kindle 2 since May 2009, I can testify to the allure of this feature: I’ve bought a couple of dozen more e-books for my Kindle than I would ever have ordered from Amazon in print form in the same period.
Today’s wireless e-reading devices fall into two groups, each with its strong points. The “electronic ink” devices all use black-and-white electrophoretic displays manufactured by Prime View International. (The Taiwanese display maker acquired the company that developed the technology, MIT spinoff E Ink, in 2009.) The $259 Kindle 2 is the best-known of these products, but Barnes and Noble’s identically priced Nook and the $400 Sony Reader Daily Edition offer similar functions. The Kindle DX ($489) and the forthcoming Plastic Logic Que proReader (expected this summer, starting at $649) have larger screens and are intended mainly for reading textbooks and business documents. The Prime View screens on these devices depend on reflected ambient light, which gives them two advantages: they’re easier on the eyes than backlit LCD screens, and they use far less power. Their batteries can last for days, and sometimes weeks, between charges.
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by Ina Fried
A start-up has plans to turn the traditional approach to blade servers on its ear, and it’s not just smoke and mirrors. But it is light and mirrors.
For the past seven years, Lightfleet has been working on a technology that employs light signals to replace the cabling and switches typically used to connect various server nodes in a blade server. And as of December, it had delivered its first unit–to Microsoft’s Research’s labs.
Lightfleet’s first product is code-named Beacon, a 32-node server that uses dual-core Intel processors along with standard off-the-shelf disks, memory, and storage all in a package that stands about 16 inches tall on a server rack (9U in server speak).
What’s different is the way each node talks to the others, the so-called interconnections within the server. Although not typically the sexiest part of computing, the interconnections in a server blade play a critically important part in determining not just how fast it that server runs, but also how much power the whole data center uses and how much heat it throws off.
Just improving performance is a big deal. No matter how fast the chips and memory inside servers get, there is always the challenge of how fast one can connect the different nodes together. And, historically, the more nodes you put in a blade server, the more complex that job of interconnection gets.
But that’s not the case with Lightfleet’s approach. The company’s motto–all to all, all at once–may sound like a bad reinterpretation of the Three Musketeers’ slogan, but it’s the key to how the company gets around the standard bottleneck.
Instead of having to pass the message from one server to the next or use a switch to route the various signals, each of Lightfleet’s server nodes can broadcast the signal to all the others, and each node can receive the signal sent by every other node’s transmitters.
Think of traditional signaling as trying to make a series of messenger deliveries throughout Manhattan. Whether you have a Ferrari or a Pinto, you are only going to move so fast through traffic. And even if you have a fleet of cars, things will only speed up so much. Plus you have the hassle of distributing all the packages.
Lightfleet’s approach, meanwhile, is more akin to being able to deliver the messages by beaming them from rooftop to rooftop.
On the technical side, the receivers work a bit like a tiny video camera, capturing all of the light signals that come in so that something known as a demultiplexer can then translate the signals into a bunch of ones and zeroes.
Lightfleet is, of course, not the first to use optics for signal transmission. Fiber optics also take advantage of the fact that light moves faster than just about anything else. But with fiber optics, you’ve still got the signal only traveling from one point to another. With Lightfleet’s approach, each node can talk to all 32 nodes at once.
(Intel, meanwhile, proposes a technology called Light Peak that be used to connect PCs to all manner of peripherals.)
Based based in the tiny Pacific Northwest town of Camas, Wash., Lightfleet is still in its infancy, even after seven years of work. The company, which got angel funding in 2006, has just 22 employees and expects to ship just a handful of systems this year.
“We want to really support our customers this year and make sure each of them gets the maximum benefit,” said CEO John Peers. At the same time, he said, “You want to put out enough that we prove the claims we’re making.”
Still, the company hopes to follow in the footsteps of its far more famous customer and fellow resident of the Evergreen State.
“We hope to do to Camas what a certain company did to Redmond,” Peers said.
Lightfleet ended up with Microsoft as its first customer a bit by accident. Some folks on Wall Street had heard about Lightfleet’s technology and were interested in seeing it for themselves. Microsoft got wind of it and asked the company to stop by its New York offices while they were in town. Pretty soon, the colossus of Redmond was Lightfleet’s first customer.
“We would have given our right arm to give it to these folks but they were good enough to buy it,” Peers said.
A one-atom thick sheet of graphene (highlighted in the circular window) on top of a silicon dioxide support proves to be an excellent thermal conductor, according to new research published in the journal Science. Although the interaction with the silicon dioxide suppressed the thermal conductivity of graphene compared to its freestanding form, supported graphene still demonstrated much higher heat conducting capability than silicon and copper nanostructures. This finding combined with graphene’s superior strength and electron mobility make it a promising candidate for use in next-generation nano-electronic devices. (Credit: University of Texas at Austin)
The single-atom thick material graphene maintains its high thermal conductivity when supported by a substrate, a critical step to advancing the material from a laboratory phenomenon to a useful component in a range of nano-electronic devices, researchers report in the April 9 issue of the journal Science.
The team of engineers and theoretical physicists from the University of Texas at Austin, Boston College, and France’s Commission for Atomic Energy report the super-thin sheet of carbon atoms — taken from the three-dimensional material graphite — can transfer heat more than twice as efficiently as copper thin films and more than 50 times better than thin films of silicon.
Since its discovery in 2004, graphene has been viewed as a promising new electronic material because it offers superior electron mobility, mechanical strength and thermal conductivity. These characteristics are crucial as electronic devices become smaller and smaller, presenting engineers with a fundamental problem of keeping the devices cool enough to operate efficiently.
The research advances the understanding of graphene as a promising candidate to draw heat away from “hot spots” that form in the tight knit spaces of devices built at the micro and nano scales. From a theoretical standpoint, the team also developed a new view of how heat flows in graphene.
When suspended, graphene has extremely high thermal conductivity of 3,000 to 5,000 watts per meter per Kelvin. But for practical applications, the chicken-wire like graphene lattice would be attached to a substrate. The team found supported graphene still has thermal conductivity as high as 600 watts per meter per Kelvin near room temperature. That far exceeds the thermal conductivities of copper, approximately 250 watts, and silicon, only 10 watts, thin films currently used in electronic devices.
The loss in heat transfer is the result of graphene’s interaction with the substrate, which interferes with the vibrational waves of graphene atoms as they bump against the adjacent substrate, according to co-author David Broido, a Boston College Professor of Physics.
The conclusion was drawn with the help of earlier theoretical models about heat transfer within suspended graphene, Broido said. Working with former BC graduate student Lucas Lindsay, now an instructor at Christopher Newport University, and Natalio Mingo of France’s Commission for Atomic Energy, Broido re-examined the theoretical model devised to explain the performance of suspended graphene.
“As theorists, we’re much more detached from the device or the engineering side. We’re more focused on the fundamentals that explain how energy flows through a sheet graphene. We took our existing model for suspended graphene and expanded the theoretical model to describe this interaction that takes place between graphene and the substrate and the influence on the movement of heat through the material and, ultimately, it’s thermal conductivity.”
In addition to its superior strength, electron mobility and thermal conductivity, graphene is compatible with thin film silicon transistor devices, a crucial characteristic if the material is to be used in low-cost, mass production. Graphene nano-electronic devices have the potential to consume less energy, run cooler and more reliably, and operate faster than the current generation of silicon and copper devices.
Broido, Lindsay and Mingo were part of a research team led by Li Shi, a mechanical engineering professor at the University of Texas at Austin, which also included his UT colleagues Jae Hun Seol, Insun Jo, Arden Moore, Zachary Aitken, Michael Petttes, Xueson Li, Zhen Yao, Rui Huang, and Rodney Ruoff.
The research was supported by the Thermal Transport Processes Program and the Mechanics of Materials Program of the National Science Foundation, the U.S. Office of Naval Research, and the U.S. Department of Energy Office of Science.
Adapted from materials provided by Boston College.
- Jae Hun Seol, Insun Jo, Arden L. Moore, Lucas Lindsay, Zachary H. Aitken, Michael T. Pettes, Xuesong Li, Zhen Yao, Rui Huang, David Broido, Natalio Mingo, Rodney S. Ruoff, and Li Shi. Two-Dimensional Phonon Transport in Supported Graphene. Science, 2010; 328 (5975): 213 DOI: 10.1126/science.1184014
The centerpiece of the new microlaser is the electric resonator, consisting of two semi-circular capacitors that are connected via an inductor (here, a scanning electron microscope image). The color intensity represents the strength of the electrical field; the color itself, the respective polarity. (Credit: Photo: ETH Zurich)
ETH-Zurich physicists have developed a new kind of laser that shatters the boundaries of possibility: it is by far the smallest electrically pumped laser in the world and one day could revolutionize chip technology.
It took a good one and a half years from the idea to its inception; a time when Christoph Walther, a PhD student in the Quantum Optoelectronics Group at ETH Zurich, spent days and nights in the FIRST lab. This was because ETH Zurich’s state-of-the-art clean-room facility provided him with the ideal conditions to set a new record in laser technology: the physicist teamed up with four colleagues and developed the smallest electrically pumped laser in the world to date.
Much smaller than the wavelength
It’s 30 micrometers long — that’s 30 millionths of a meter — eight micrometers high and has a wavelength of 200 micrometers. This makes the laser considerably smaller than the wavelength of the light it emits — a scientific first. After all, lasers normally can’t be smaller than their wavelength, the reason being that in conventional lasers light waves cause an optic resonator to oscillate — much like acoustic waves do to the soundbox of a guitar. In doing so, the light waves basically “travel” back and forth between two mirrors. The principle only works if the mirrors are larger than the wavelength of the laser. Consequently, normal lasers are limited in terms of their size.
Other researchers have endeavored to push the boundaries; “But by developing a completely new laser concept we were able to go quite a way below the limit,” says Christoph Walther.
Inspired by electronics
In developing their laser concept, Christoph Walther and some of his team mates under his supervisor Jérôme Faist, professor and head of ETH Zurich’s Institute of Quantum Electronics, were inspired by electronics. “Instead of the usual optic resonators, we use an electrical resonant circuit made up of an inductor and two capacitors,” explains Walther. The light is effectively “captured” in it and induced into self-sustaining electromagnetic oscillations on the spot using an optical amplifier.
“This means the size of the resonator is no longer limited by the wavelength of the light and can in principle — and that’s what makes it so special — be scaled down to whatever size you want.” This prospect especially makes the microlaser interesting for chip manufacturers — as an optic alternative to the transistors. “If we manage to approximate the transistors in terms of size using the microlasers, one day they could be used to build electro-optic chips with an extremely high concentration of electronic and optic components,” says Christoph Walther. These could one day considerably speed up the exchange of data on microprocessors.
Adapted from materials provided by ETH Zurich.
- Walther et al. Microcavity Laser Oscillating in a Circuit-Based Resonator. Science, 2010; 327 (5972): 1495 DOI: 10.1126/science.1183167
By adjusting an electrical voltage across a crystal of nonlinear material, the researchers recovered an image of lines and numbers that originally was hidden in noise (upper left). As they tuned the system (from left to right across each row from top to bottom), the image “stole” energy from the noise, first appearing and then degrading as they adjusted past the optimal voltage. (Credit: Jason Fleischer/Dmitry Dylov)
A new technique for revealing images of hidden objects may one day allow pilots to peer through fog and doctors to see more precisely into the human body without surgery.
Developed by Princeton engineers, the method relies on the surprising ability to clarify an image using rays of light that would typically make the image unrecognizable, such as those scattered by clouds, human tissue or murky water.
In their experiments, the researchers restored an obscured image into a clear pattern of numbers and lines. The process was akin to improving poor TV reception using the distorted, or “noisy,” part of the broadcast signal.
“Normally, noise is considered a bad thing,” said Jason Fleischer, an assistant professor of electrical engineering at Princeton. “But sometimes noise and signal can interact, and the energy from the noise can be used to amplify the signal. For weak signals, such as distant or dark images, actually adding noise can improve their quality.”
He said the ability to boost signals this way could potentially improve a broad range of signal technologies, including the sonograms doctors use to visualize fetuses and the radar systems pilots use to navigate through storms and turbulence. The method also potentially could be applied in technologies such as night vision goggles, inspection of underwater structures such as levies and bridge supports, and in steganography, the practice of masking signals for security purposes.
The findings were reported online March 14 in Nature Photonics.
In their experiments, Fleischer and co-author Dmitry Dylov, an electrical engineering graduate student, passed a laser beam through a small piece of glass engraved with numbers and lines, similar to the charts used during eye exams. The beam carried the image of the numbers and lines to a receiver connected to a video monitor, which displayed the pattern.
The researchers then placed a translucent piece of plastic similar to cellophane tape between the glass plate and the receiver. The tape-like material scattered the laser light before it arrived at the receiver, making the visual signal so noisy that the number and line pattern became indecipherable on the monitor, similar to the way smoke or fog might obstruct a person’s view.
The crucial portion of the experiment came when Fleischer and Dylov placed another object in the path of the laser beam. Just in front of the receiver, they mounted a crystal of strontium barium niobate (SBN), a material that belongs to a class of substances known as “nonlinear” for their ability to alter the behavior of light in strange ways. In this case, the nonlinear crystal mixed different parts of the picture, allowing signal and noise to interact.
By adjusting an electrical voltage across the piece of SBN, the researchers were able to tune in a clear image on the monitor. The SBN gathered the rays that had been scattered by the translucent plastic and used that energy to clarify the weak image of the lines and numbers.
“We used noise to feed signals,” Dylov said. “It’s as if you took a picture of a person in the dark, and we made the person brighter and the background darker so you could see them. The contrast makes the person stand out.”
The technique, known as “stochastic resonance,” only works for the right amount of noise, as too much can overwhelm the signal. It has been observed in a variety of fields, ranging from neuroscience to energy harvesting, but never has been used this way for imaging.
Based on the results of their experiment, Fleischer and Dylov developed a new theory for how noisy signals move through nonlinear materials, which combines ideas from the fields of statistical physics, information theory and optics.
The research was funded by the National Science Foundation, the U.S. Department of Energy and the U.S. Air Force.
Their theory provides a general foundation for nonlinear communication that can be applied to a wide range of technologies. The researchers plan to incorporate other signal processing techniques to further improve the clarity of the images they generate and to apply the concepts they developed to biomedical imaging devices, including those that use sound and ultrasound instead of light.
Adapted from materials provided by Princeton University, Engineering School.
- Dylov et al. Nonlinear self-filtering of noisy images via dynamical stochastic resonance. Nature Photonics, 2010; DOI: 10.1038/nphoton.2010.31