Light through a blocked hole? Plasmonics is the answer

How would you react if a tiny hole in a piece of foil let through more light after you had covered it – or painted the foil a different colour?

With surprise, probably, like the physicists who discovered that this is just what happens with some very small holes. Both findings could lead to light-based transistors and other components for high-speed optical computers.

Conventional optics forbids light from passing through holes that are much smaller than its wavelength, which for visible light means less than around 400 nanometres wide. But in 1998, Thomas Ebbesen at the University of Strasbourg, France, reported that some wavelengths of visible light stream through holes in gold foil that are less than 300 nanometres wide.

It turns out that this is due to ripples known as plasmons that are found on the surface of metals and formed by the oscillation of electrons.

Total eclipse

If the frequency of light hitting the surface of a metal happens to match the oscillation of that metal's surface electrons, the plasmons grab the photons, guide them through the holes and release them on the other side. The plasmons on gold surfaces, for example, are particularly adept at interacting with visible light.

Now a team led by Hiromi Okamoto at the Institute for Molecular Science in Okazaki, Japan, have found another way to coax photons through tiny holes – paradoxically, by obscuring the hole with a gold disc.

The team was shining light down an optical fibre that tapered to a 100-nanometre-wide aperture. At first, barely any light made it through the aperture; instead, it was reflected back up the fibre. But when the researchers placed a small gold disc very close to the aperture, so that it completely eclipsed the hole without actually touching it, the light started streaming through (see graphic, right).

They suspect that plasmons from the gold disc are leaping up through the hole, grabbing the photons stuck inside the fibre and dragging them through. These photons then stream around the edges of the disc.

Dye enhancement

Okamoto's team found that if the disc touched the hole, the effect did not work; widening the disc, however, caused still more light to come through. "When we observed that the larger disc gives higher transmission, we were really surprised," Okamoto says.

This ability to open or block a hole to light could be useful when building components for optical computers, which transmit signals using light instead of electrons.

"The novelty is in controlling this transmission with various 'caps'," saysDmitry Skryabin, a nanophotonics researcher at Bath University in the UK.

Light transmission through a tiny hole can also be controlled with dyes, as Ebbesen and his colleague James Hutchison, also at the University of Strasbourg, recently found.

Plasmon passing

Normally, when white light is shone onto a piece of gold foil pierced with tiny holes, only the wavelengths of green light pass through. But Ebbesen and Hutchison found that coating the foil with a thin layer of green dye allowed red light to pass through as well; indeed, more red than green started to come through.

This was a shock, as green dye should absorb all light except green. "One certainly doesn't expect a sample to become transparent at the wavelengths where the molecule absorbs," says Hutchison.

The researchers suspect that the dye molecules absorb the red light but then "pass" it to the plasmons underneath the dye, which are not of the right frequency to interact with red light directly.

Hutchison says that holes painted with various dyes could also be useful in optical computing components.

Journal references: Nano Letters, DOI: 10.1021/nl103408h; Angewandte Chemie, DOI: 10.1002/anie.201006019

Source:http://www.newscientist.com/article/dn20116-light-through-a-blocked-hole-plasmonics-is-the-answer.html?DCMP=OTC-rss&nsref=online-news

"Big Bang" scientists map cautious plan for 2011

Scientists at the CERN research center seeking answers to key mysteries of the cosmos said on Wednesday they would be moving ahead cautiously this year to avoid any possible breakdown in their giant LHC machine.

But they indicated that in 2012, if all goes well, they would step up the energy of particle collisions that most feel is vital to bring them near to finding the almost mythical Higgs boson and evidence for the existence of dark matter.

"We are pushing the limits," physicist Marco Zanetti told a seminar for CERN staff attended by Reuters.

Simulations of what could happen if there was a simple leak in a joint in the hugely complex machine like the incident that set back the LHC project by a year in 2009 showed it could bring another 12-month delay, he said.

But Zanetti and other speakers at the seminar made clear they saw little chance of this happening now the LHC -- or Large Hadron Collider -- has been functioning without a glitch since March 31 last year.

After a two-month winter shutdown, it is starting up again later this month -- with the particle collisions that simulate the primeval explosion that created the universe 13,7 billion years ago at the top energy yet reached for around 135 days.

That energy is called 3.5 TeV, or tera electron-volts, giving a total of 7 TeV when the particles speeding around the LHC's 27-kilometre tunnel deep under the Swiss-French border on the edge of Geneva smash into each other.

CERN technology director Steve Myers told the seminar that the LHC team still hoped to double the energy impact in 2014, after a year-long shutdown in 2013 for intensive upgrading, but the next few months would show if that were viable.

At the higher collision energy of 14 TeV, CERN -- the 21-nation European Organization for Particle Research -- expects to produce results that could shed light on the possible existence of parallel worlds or multiple universes.

Originally the LHC had been due to shut down at the end of this year for 12 months but the CERN council decided last month to keep going through 2012 because the machine was running so smoothly, giving extra time for an early discovery.

The Higgs -- the particle whose existence was posited nearly 40 years ago by British scientist Peter Higgs as the mystery agent that turns mass into matter and makes the known universe work -- is the prime target at this phase.

Source:http://news.feedzilla.com/en_us/stories/top-news/science/57415710?count=20&client_source=feedzilla_widget&order=relevance&format=json&sb=1

Scientists make nanosheets with high-tech potential

A novel way of splitting materials into sheets just one atom thick could lead to new electronic and energy storage technologies, scientists said Thursday.

An international team of researchers said they had invented a versatile way to create one atom thick "nanosheets" from a range of layered materials, similar to the graphite used in pencils, using ultrasonic pulses and common solvents.

The new method is simple, cheap, fast, and could be scaled up to work on an industrial scale, the scientists said in a report of their work published in the journal Science.

The research adds to previous studies by two Russian-born scientists, who last year won the Nobel Prize for physics for their work on graphene, a form of carbon that is just one atom thick and yet 100 times stronger than steel.

"Because of its extraordinary electronic properties graphene has been getting all the attention...as physicists hope that it might one day compete with silicon in electronics," said Valeria Nicolosi, of Britain's Oxford University, who led the study with Jonathan Coleman of Ireland's Trinity College Dublin.

"But in fact there are hundreds of other layered materials that could enable us to create powerful new technologies."

Coleman said the new materials this team had created -- which include Boron Nitride, Molybdenum disulfide, and Bismuth telluride -- have chemical and electronic properties which make them suitable for use in new electronic devices, super-strong composite materials and energy generation and storage.

"Of the many possible applications of these new nanosheets, perhaps the most important are as thermoelectric materials," he said in a statement about the findings.

He said the materials could for example be made into devices that generate electricity from waste heat lost from places like gas, oil or coal-fired power plants, which lose between 50 and 70 percent of the energy they produce in waste heat.

"The development of efficient thermoelectric devices would allow some of this waste heat to be recycled cheaply and easily," Coleman said.

Scientists have been trying for decades to create nanosheets of these kind of materials, because arranging them in atom-thick layers enables their unusual electronic and thermoelectric properties to be unlocked, the researchers explained.

But all previous methods were very time consuming and laborious, and the resulting materials were fragile and not suitable for most applications.

"Our new method offers low-costs, a very high yield and a very large throughput -- within a couple of hours, and with just 1 milligram of material, billions and billions of one-atom-thick graphene-like nanosheets can be made at the same time from a wide variety of exotic layered materials," said Nicolosi.

These new materials could also be used in next generation batteries known as "supercapacitors," which can deliver energy thousands of times faster than standard batteries and could vastly improve technologies such as electric cars.

Source:http://www.reuters.com/article/2011/02/03/us-science-nanosheets-idUSTRE7127EB20110203?feedType=RSS&feedName=scienceNews&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+reuters/scienceNews+(News+/+US+/+Science)

Laser blasts sunlight protein into view

(Image: Thomas White/DESY)

Meet photosystem I, a plant protein that converts sunlight into energy during photosynthesis, in all its crystalline glory.

To create this image, researchers led by Henry Chapman of the Centre for Free-Electron Laser Science at the German national laboratory DESY sprayed 15,000 nanocrystals of the protein into the path of the Linac Coherent Light Source, an X-ray laser at the SLAC National Accelerator Laboratory in Menlo Park, California.

Powerful laser pulses vaporised the nanocrystals almost instantly, but not before the crystals had scattered X-rays, producing diffraction patterns that could be combined to render the crystal's detailed structure in three dimensions.

The ability to glean structural data from such tiny crystals could allow many more proteins to be understood. Other methods of elucidating structure require larger crystals, which, for some proteins, can be difficult or impossible to prepare.

Journal reference: Nature, DOI:10.1038/nature09750

Caffeinated Gene Therapy

Many people in society simply cannot function without a daily dose of caffeine. It is so prevalent in many diets. From coffee, to tea, to soft drinks, it has become a staple on par with corn or wheat, or even water. Of course caffeine is not necessary to survive, but it is sure good at keeping our eyes open. However, according to a new study from researchers at the University of Texas, caffeine does more than just keep us awake. It also energizes cells into producing more viruses used for gene therapy.

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Caffeine is the world's most widely consumed psychoactive substances, and amazingly, is completely legal and unregulated. It is found naturally in many plant species such as coffee, tea, and cocoa beans. Plants generate it because it paralyzes and kills certain insects which feed upon them. Therefore, it is the only stimulate we consume that is also a pesticide.

However, the amazing new property discovered by researchers can have lasting impacts on gene therapy research. Gene therapy is the manipulation of genes within the body's tissue cells with the goal of treating disease. It can correct defective genes which are responsible for disease development.

The problem is how to manipulate the genes. For a long time, scientists have known that viruses reproduce by binding to their hosts and introducing their unique genetic material into the cell. This genetic material gives instructions to the cell to produce copies of itself, hijacking the cell’s natural production. For gene therapists, viruses can be used to manipulate cells with "good" genetic material. This is known as the viral vector.

The new study recently published in the journal Human Gene Therapy claims that caffeinated cells used to produce viruses for gene therapy can generate up to 8 times more than non-caffeinated cells. According to the researchers, using caffeine should decrease the cost of producing lentiviruses for research and clinical uses. Lentiviruses are a common type of virus used in gene therapy.

"It is ironic that the ingredient in beverages like colas and coffees that helps keep us awake and alert is also useful in jazzing up cells to produce more gene therapy vectors. An increase in vector production of 5-fold may prove critical in establishing the commercial viability of lentiviral based products," says James M. Wilson, MD, PhD, and Director of the Gene Therapy Program.

The researchers emphasize that the timing of introducing caffeine into cells is critical for increased virus production. Also the concentration of caffeine cannot be too high because it can be toxic to the cells, and would not cause them to increase virus production.

Researchers involved with the study from the University of Texas Southwestern Medical Center, Dallas include Brian Ellis, Patrick Ryan Potts, and Matthew Porteus. Their work can be found in the journal Human Gene Therapy which is published by Mary Ann Liebert, Inc.

Link to published article: http://www.liebertpub.com/contentframe.aspx?code=MDoqsls2tWBQ0c%2bZWT0nPtZ1zyJ60HXWr8kmqZBHbUfkxIBDwf3RDtPbRDToWe2xigdyewz

source:http://www.enn.com/top_stories/article/42297

'Air laser' may sniff bombs, pollutants from a distance (w/ Video)

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Researchers at Princeton University developed a technique for generating a laser beam out of nothing but air. They focus a pump laser on a distant point in the air and another laser beam comes back. The image shows a pulse of infra-red light from this "air laser." The center region represents the highest intensity; the outer areas have lower intensity light. The technique could be used for sensing minute quantities of gas in the air from a distance. Credit: Image courtesy Arthur Dogariu, Princeton University

Princeton University engineers have developed a new laser sensing technology that may allow soldiers to detect hidden bombs from a distance and scientists to better measure airborne environmental pollutants and greenhouse gasses.

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"We are able to send a laser pulse out and get another pulse back from the air itself," said Richard Miles, a professor of mechanical and aerospace engineering at Princeton, the research group leader and co-author on the paper. "The returning beam interacts with the molecules in the air and carries their finger prints."

The new technique differs from previous remote laser-sensing methods in that the returning beam of light is not just a reflection or scattering of the outgoing beam. It is an entirely new laser beam generated by oxygen atoms whose electrons have been "excited" to high energy levels. This "air laser" is a much more powerful tool than previously existed for remote measurements of trace amounts of chemicals in the air.

The researchers, whose work is funded by the Office of Naval Research's basic research program on Sciences Addressing Asymmetric Explosive Threats, published their new method Jan. 28 in the journal Science.

Miles collaborated with three other researchers: Arthur Dogariu, the lead author on the paper, and James Michael of Princeton, and Marlan Scully, a professor with joint appointments at Princeton and Texas A&M University.

Researchers at Princeton University developed a technique for generating a laser beam out of nothing but air. They focus a pump laser on a distant point in the air and another laser beam comes back. The video shows 100 pulses of infra-red light from this "air laser." The center region represents the highest intensity; the outer areas have lower intensity light. The technique could be used for sensing minute quantities of gas in the air from a distance. Credit: Image courtesy Arthur Dogariu, Princeton University

The new laser sensing method uses an ultraviolet laser pulse that is focused on a tiny patch of air, similar to the way a magnifying glass focuses sunlight into a hot spot. Within this hot spot – a cylinder-shaped region just 1 millimeter long – oxygen atoms become "excited" as their electrons get pumped up to high energy levels. When the pulse ends, the electrons fall back down and emit infrared light. Some of this light travels along the length of the excited cylinder region and, as it does so, it stimulates more electrons to fall, amplifying and organizing the light into a coherent laser beam aimed right back at the original laser. 

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Researchers plan to use a sensor to receive the returning beam and determine what contaminants it encountered on the way back.

"In general, when you want to determine if there are contaminants in the air you need to collect a sample of that air and test it," Miles said. "But with remote sensing you don't need to do that. If there's a bomb buried on the road ahead of you, you'd like to detect it by sampling the surrounding air, much like bomb-sniffing dogs can do, except from far away. That way you're out of the blast zone if it explodes. It's the same thing with hazardous gases – you don't want to be there yourself. Greenhouse gases and pollutants are up in the atmosphere, so sampling is difficult."

The most commonly used remote laser-sensing method, LIDAR -- short for light detection and ranging -- measures the scattering of a beam of light as it reflects off a distant object and returns back to a sensor. It is commonly used for measuring the density of clouds and pollution in the air, but can't determine the actual identity of the particles or gases. Variants of this approach can identify contaminants, but are not sensitive enough to detect trace amounts and cannot determine the location of the gases with much accuracy.

The returning beam is thousands of times stronger in the method developed by the Princeton researchers, which should allow them to determine not just how many contaminants are in the air but also the identity and location of those contaminants.

The stronger signal should also allow for detection of much smaller concentrations of airborne contaminants, a particular concern when trying to detect trace amounts of explosive vapors. Any chemical explosive emits various gases depending on its ingredients, but for many explosives the amount of gas is miniscule.

While the researchers are developing the underlying methods rather than deployable detectors, they envision a device that is small enough to be mounted on, for example, a tank and used to scan a roadway for bombs.

So far, the researchers have demonstrated the process in the laboratory over a distance of about a foot and a half. In the future they plan to increase the distance over which the beams travel, which they note is a straightforward matter of focusing the beam farther way. They also plan to fine-tune the sensitivity of the technique to identify small amounts of airborne contaminants.

In addition, the research group is developing other approaches to remote detection involving a combination of lasers and radar.

"We'd like to be able to detect contaminants that are below a few parts per billion of the air molecules," Miles said. "That's an incredibly small number of molecules to find among the huge number of benign air molecules."

Source:http://www.physorg.com/news/2011-01-air-laser-pollutants-distance-video.html

HOLOGRAPHIC PRINCESS LEIA NEARS REALITY

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MIT's holograms are fast, but they have to trade quality for speed. Click to enlarge this image. 
James D. Barabas/MIT

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The Force is strong with holographic scientists these days. Researchers from MIT unveiled the fastest 3-D holographic video to date at a conference in San Francisco January 23, filming a graduate student dressed as Princess Leia and projecting her as a postcard-sized hologram in real time.

The holographic device plays a 3-inch projection at 15 frames per second, just shy of movie refresh rates of 24 to 30 frames per second, the MIT researchers demonstrated at the Society of Photo-Optical Instrumentation Engineers’ conference on practical holography.

The red hologram is jerkier and has much lower resolution than the one in Star Wars that sparked the public fascination with 3-D holograms in the 1970s. In fact, it kind of looks like a red blob on a staticky TV. But it’s 30 times faster than a telepresence device created in 2010 by University of Arizona researchers (SN Online: 12/4/10).

“I think it’s an important milestone because they were able to get to 15 frames per second, which is almost real time,” says physicist Nasser Peyghambarian, who led the Arizona research. “The quality is not as high, but hopefully it will get better in the future.”

The key to speed was computational power. The MIT team used a Kinect camera from an Xbox 360 gaming console to capture light from a moving object. Then they relayed the data over the Internet to a PC with three graphics processing units, or GPUs, tiny processors found in computers, cell phones, and video games that render video quickly. The processors compute how light waves interfere with each other to form patterns of light and dark fringes. Light bouncing off these fringe patterns reconstructs the original image. The MIT team used a display to illuminate the computer-generated fringes and create a hologram.

“The students were able to figure out how to generate holograms by using what GPU chips are good at,” says Michael Bove, an MIT engineer who led the research. “And they get faster every year. There’s room for a lot more understanding of how to compute holograms on them.”

MIT’s holograms are fast, says Peyghambarian, but they have to trade quality for speed.

Bove’s device uses one camera that estimates the depth of the object it is filming. The disadvantage of one camera, which is more consumer-friendly, is that you can’t see behind objects, says Bove. Also, even though graphics cards can compute high-resolution holograms, the effective display size is limited by a chip in the physical display to 150 millimeters by 75 millimeters, which Bove says is the biggest challenge to creating better holograms.

The Arizona device had a very different setup: Researchers grabbed video from 16 cameras angled around the object, so that one could walk around a holographic person and see not just the front side, but side profiles and back views. The team used an old-fashioned method that hologram artists have employed for decades, employing two lasers to create fringe patterns. Their key insight was engineering a special type of plastic that erases and rewrites quickly. The Arizona hologram is already high-definition and the size of a 17-inch TV, but speeding it up will require switching to a new laser system, says Peyghambarian.

“There’s a variety of technologies,” says Bove. “The fact is, the barrier to entry has been unbelievably high for the past 20 years. Now, many technologies are maturing at the same time. I think we’ll see some fun things in the next few years.”

Bove looks to the near future for consumer teleconferencing that connects people far, far away from each other, just like Darth Vader and the Emperor in their imperial chats. Star Wars purists will remember that Princess Leia’s plea was actually prerecorded.

Source:http://news.discovery.com/tech/hologram-princess-leia-3d-110127.html#mkcpgn=rssnws1