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Physicists discover new form of light, validate decades-old quantum mechanics prediction

Physicists discover new form of light, validate decades-old quantum mechanics prediction | Amazing Science | Scoop.it

It’s been over 340 years since Danish physicist Ole Rømer observed that the speed of light was finite. And, to this day, photons still manage to surprise us. Last year, scientists revealed a new fundamental property of light. This year, a team of physicists from by the Trinity College Dublin and the CRANN Institute have just discovered a new form of light that refuses to behave normally, and undermines what physicists know about angular momentum.

 

“Angular momentum measures how much something is rotating,” one of the study’s researchers, Kyle Ballantine, told Trinity News. “For a beam of light, although traveling in a straight line it can also be rotating around its own axis.” Up until this finding, physicists thought the angular momentum of all forms of light was a multiple of Planck’s constant. Apparently, that’s not so.

 

To uncover this information, the researchers began by searching for new behaviors of light by shining beams through crystals to create “screw-like structures.” They used the theory of quantum mechanics to analyze these beam structures and realized that the angular momentum of the photon would be a half-integer, not a multiple of Planck’s constant.

 

This discovery might not sound like much, but researchers suggest that it will influence our knowledge about the very essence of light. “Our discovery will have real impacts for the study of light waves in areas such as secure optical communications,” Professor John Donegan said.

 

Finding a new form of light is undoubtedly exciting. However, much of the physics community’s real joy comes from validating 30-year-old theoretical physics predictions. In the 1980s, physicists speculated ways in which quantum mechanics would open doors for strange new discoveries, such as particles with fractions of their expected quantum numbers. This research provides the first validation of those predictions. “This discovery is a breakthrough for the world of physics and science alike,” said CRANN Director, Stefano Santo.

 


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Twisted light could dramatically boost internet speeds - by 6 orders of magnitude

Twisted light could dramatically boost internet speeds - by 6 orders of magnitude | Amazing Science | Scoop.it

Fiber optics allow for the communication of data at the speed of light. But the amount of data that can be sent along any optic fiber is limited by how much information you can encode into the light wave travelling through it. Currently, optic fiber technology uses several different properties of light to encode information, including brightness, color, polarization and direction of propagation. But if we want to cram even more information through optic fiber, we need to use other features of light to encode more information, without disrupting the currently used properties. Such a feature could help boost the bandwidth of optic fiber technology, including our internet speed.

 

If the light wave travelling through the optic fiber is twisted helically – like a spring – then it has an angular momentum, which is a measure of its momentum when it rotates around a point. But there was a major problem with using angular momentum to decode the information from the optic fiber in the past. We needed a material with tiny nanoscale helical structures that could detect the twisted light when present.

A research team now published in Science, how the angular momentum of light at a nanoscale can be controlled by using an integrated photonic chip. So for the first time, we have a chip with a series of elaborate nano-apertures and nano-grooves that allow for the on-chip manipulation of twisted light.

 

The helical design of these tiny apertures and grooves removes the need for any other bulky interference-based optics to detect the angular momentum signals. So if you send an optical data signal to a photonic chip, which is a microchip that uses light instead of electrons, then it is important to know where the data is going, otherwise information will be lost. Using this type of a nanophotonic chip, the researchers could precisely guide angular momentum data signals without losing the information they carry. What’s more, the angular momentum information of many different signals can be processed at the same time through the chip. This means we can potentially achieve an ultra-wide bandwidth, with six orders of magnitude of increased data access compared to current technology.

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Triple entanglement in three dimensions: Three "twisted" photons entangled

Triple entanglement in three dimensions: Three "twisted" photons entangled | Amazing Science | Scoop.it

Researchers at the Institute of Quantum Optics and Quantum Information (IQOQI), the University of Vienna, and the Universitat Autonoma de Barcelona have achieved a new milestone in quantum physics: they were able to entangle three particles of light in a high-dimensional quantum property related to the "twist" of their wavefront structure. Just like Schrödinger's famous cat that is simultaneously dead and alive, all previous demonstrations of multi-particle entanglement have been with quantum objects in two discrete levels, or dimensions. The twisted photons used in the Vienna experiment have no such limit to their dimensionality, and can simultaneously exist in three or more quantum states. The three-photon entangled state created by the Vienna group breaks this previous record of dimensionality, and brings to light a new form of asymmetric entanglement that has not been observed before. The results from their experiment appear in the journal Nature Photonics.

Entanglement is a counterintuitive property of quantum physics that has long puzzled scientists and philosophers alike. Entangled quanta of light seem to exert an influence on each other, irrespective of how much distance is between them. Consider for example a metaphorical quantum ice dancer, who has the uncanny ability to pirouette both clockwise and counter-clockwise simultaneously. A pair of entangled ice-dancers whirling away from each other would then have perfectly correlated directions of rotation: If the first dancer twirls clockwise then so does her partner, even if skating in ice rinks on two different continents. "The entangled photons in our experiment can be illustrated by not two, but three such ice dancers, dancing a perfectly synchronized quantum mechanical ballet," explains Mehul Malik, the first author of the paper. "Their dance is also a bit more complex, with two of the dancers performing yet another correlated movement in addition to pirouetting. This type of asymmetric quantum entanglement has been predicted before on paper, but we are the first to actually create it in the lab."

The scientists created their three-photon entangled state by using yet another quantum mechanical trick: they combined two pairs of high-dimensionally entangled photons in such a manner that it became impossible to ascertain where a particular photon came from. Besides serving as a test bed for studying many fundamental concepts in quantum mechanics, multi-photon entangled states such as these have applications ranging from quantum computing to quantum encryption. Along these lines, the authors of this study have developed a new type of quantum cryptographic protocol using their state that allows different layers of information to be shared asymmetrically among multiple parties with unconditional security. "The experiment opens the door for a future quantum Internet with more than two partners and it allows them to communicate more than one bit per photon," says Anton Zeilinger. Many technical challenges remain before such a quantum communication protocol becomes a practical reality. However, given the rapid progress in quantum technologies today, it is only a matter of time before this type of entanglement finds a place in the quantum networks of the future.

Publication in "Nature Photonics": Multi-Photon Entanglement in High Dimensions: Mehul Malik, Manuel Erhard, Marcus Huber, Mario Krenn, Robert Fickler, Anton Zeilinger. Nature Photonics, 2016
http://dx.doi.org/10.1038/nphoton.2016.12.

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Processor With Photonic Interconnects Built

Processor With Photonic Interconnects Built | Amazing Science | Scoop.it

Chip designers would love to use light beams rather than copper wires to move data between microprocessors. Such optical interconnects would overcome the bandwidth bottleneck inherent in the wires and take full advantage of the leaps in processor speed, but marrying two very different technologies—electronics and photonics—has been a high hurdle to overcome.


Now a group of researchers has proposed a way to build transistors and optics on the same chip, doing so for the first time without a major overhaul of the chip-making process. And they used it to build an IC containing 70 million transistors and 850 photonic components, which together provide all the logic, memory, and interconnection functions a processor needs.


Engineers at MIT, the University of California, Berkeley, and the University of Colorado, Boulder founded a start-up to commercialize what they call their “zero-change” approach to chip-making. It relies on the standard CMOS processes used to make today’s computer chips—specifically a high-performance process for the so-called 45-nanometer node, which debuted in 2007. “We didn’t make any changes to the process,” says Chen Sun, lead author of a paper on the process that appears in this week’s issue of Nature.


They started with a silicon substrate, then added a 200-nm thick layer of silicon-oxide, which acts as an insulator. Over that is the active layer—100 nm of crystalline silicon—plus a 100-nm layer of nitrides and a dielectric coating. The crystalline silicon includes a small amount of germanium to produce strain on the silicon and speed up the circuits. 


“We are able to use those existing layers to make our processors,” Sun says. The processor they constructed was a dual-core RISC-V architecture—an open instruction set architecture originally developed at Berkeley. It also included 1 megabyte of SRAM memory.


One key component to the photonics portion of the chip is a micro-ring resonator, a loop 10 micrometers across that’s coupled to a waveguide. They dope the structure with the same elements used to make p-n junctions in the transistors, and that action creates a notch filter, which passes all incoming light but a single wavelength. Putting a negative voltage across the junction pushes the charge carriers out of the ring, while a positive voltage returns them, creating a modulator that imprints digital signals on the light beam.


The micro-ring also lets the photodetector work. Normally, a photodetector made of the SiGe in the chip would have to be many millimeters to a centimeter long in order to have a chance of absorbing enough photons to actually detect the light. With the micro-ring resonator, the light passes through so many times that the SiGe can absorb it.


Micro-ring resonators have existed for a while, but “a lot of people in industry kind of ignored them,” says Sun. That’s because as they heat up, the index of refraction shifts and they drift away from the desired wavelength. The team developed active thermal stabilization to overcome this. The stabilization system includes a separate photodetector and a digital controller. When the detector notices a change in the amount of photocurrent coming to it, the controller alters the voltage across the micro-ring, which changes how much heat it dissipates.


Another aspect of the design requires etching away some of the silicon substrate. Because the oxide layer is so thin, the light passes through it to the substrate, which carries it away. Removing the substrate reduces that loss. However, the team leaves the silicon in place under the microprocessor and memory, where no light is coming out anyway, so they can attach a heat sink. The lack of silicon also allows them to deliver light from an external laser to power the optical components, even though the chip is bonded face down to the printed circuit board.

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Curved waveguide created which is able to significantly bend X-ray beams

Curved waveguide created which is able to significantly bend X-ray beams | Amazing Science | Scoop.it
A team of researchers working in Germany and France has demonstrated a way to bend X-ray beams using curved wave guides. In their paper published in Physical Review Letters, the team describes how they created the wave guides, the parameters they used in creating them and the results of their testing.


Light can be used to send signals through a fiber cable because the indices of refraction of air and glass are so different—light inside a fiber cable is reflected back into the hollow tunnel as turns are encountered. This is not the case for X-rays, however, because the index of refraction for it in solid materials is just a little bit less than for that of air. Subsequently, X-ray devices are typically extremely straight-lined. Now, the researchers with this new effort report that they have found a way to bend X-ray beams, possibly paving the way for their use in a wide variety of applications.


The key to bending X-ray beams, the team reports, is in sending them through a sufficiently narrow channel—narrow enough to limit the beam's maximum angle of deflection. Also, the device used to create the beam must be extremely precise.


To test their ideas, they created wave guides by etching 100nm wide curved channels onto 5x5mm squares of tantalum, which they then fired X-rays through. Their first runs involved radii curvatures of 10 to 80 mm with beams sent at Hamburg's DESY laboratory. In so doing, they found they were able to bend X-rays at up to 18 degrees. Emboldened, they etched more waveguides with channel radii curvatures of 1–30 mm and then tested them by firing X-rays through them at the European Synchrotron Radiation Facility in France. This time they were able to bend the beams to 30 degrees. Not all of the X-rays in the beam that are sent make it through the channel, of course, some are absorbed or tunnel their way through the metal—but, the team reports, enough makes it through for the waveguides to be useful in devices such as interferometers or other high-resolution applications.


The team plans to continue their work with the waveguides, confident that they can lessen leakage by using different materials, and possibly covering the channel. They suggest it might be possible to bend X-rays to even higher angles, from 90 to perhaps 180 degrees.

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Echoless light could help send signals through walls and skin

Echoless light could help send signals through walls and skin | Amazing Science | Scoop.it

A new method of making packets of light that don't echo inside optical fibers could be used to improve everything from medical imaging to laser communications.


It’s a call with no response. A new way of creating waves – whether of light, radio or sound – that don’t echo promises to improve everything from your Wi-Fi signal to medical imaging to shining lasers through space.


As a wave travels – think of light shining through water, for example – it can become scattered. This is a problem intelecommunications: if you send digital signals down a very long optical fibre, the pulses can get stretched out, and 1s can start to blend into 0s.


In 1948, physicist Leonard Eisenbud proposed a particular way of transmitting the waves to overcome this. But not until now have researchers made it happen. “The trick is that you put it in as a fancy shape, and then the sound doesn’t get distorted,” says Joel Carpenter at the University of Queensland in Brisbane, Australia. “There are no echoes: it arrives all at once at the output.”


The team started with a 100-metre-long fibre optic cable that was thin enough that light travelling through would bounce around inside, just as sound would if sent through a narrow pipe. When the light emerged at the other end, short pulses had become stretched out.


They measured exactly how the light was distorted, and crucially, how the profile of the pulse changed on its journey through the fibre. The profile at any cross section through the fibre could look like a round dot, a few dots or something more complicated, and it determines what path the photons take down the fibre, and how they interfere as they bounce around, Carpenter says.


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First optical rectenna—combined rectifier and antenna—converts light to DC current

First optical rectenna—combined rectifier and antenna—converts light to DC current | Amazing Science | Scoop.it
Using nanometer-scale components, researchers have demonstrated the first optical rectenna, a device that combines the functions of an antenna and a rectifier diode to convert light directly into DC current.


Based on multiwall carbon nanotubes and tiny rectifiers fabricated onto them, the optical rectennas could provide a new technology for photodetectors that would operate without the need for cooling, energy harvesters that would convert waste heat to electricity - and ultimately for a new way to efficiently capture solar energy.


In the new devices, developed by engineers at the Georgia Institute of Technology, the carbon nanotubes act as antennas to capture light from the sun or other sources. As the waves of light hit the nanotube antennas, they create an oscillating charge that moves through rectifier devices attached to them. The rectifiers switch on and off at record high petahertz speeds, creating a small direct current.


Billions of rectennas in an array can produce significant current, though the efficiency of the devices demonstrated so far remains below one percent. The researchers hope to boost that output through optimization techniques, and believe that a rectenna with commercial potential may be available within a year.


"We could ultimately make solar cells that are twice as efficient at a cost that is ten times lower, and that is to me an opportunity to change the world in a very big way" said Baratunde Cola, an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. "As a robust, high-temperature detector, these rectennas could be a completely disruptive technology if we can get to one percent efficiency. If we can get to higher efficiencies, we could apply it to energy conversion technologies and solar energy capture."

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New Type of Thermal Radiation Discovered

New Type of Thermal Radiation Discovered | Amazing Science | Scoop.it

Nano-photonics expert and physics professor Shawn-Yu Lin has discovered a new type of thermal radiation—in between the two extremes of blackbody radiation and laser light—that could contribute to a cheaper, easier solution for converting sunlight to electricity.


This “third light” is promising because it possesses some of the more favorable traits of both blackbody radiation and laser light.


Thermal radiation impacts every aspect of daily life. Two of the best-known examples are the light emitted from the sun and from incandescent light bulbs. In both cases, the light is classified as blackbody radiation. It is random and broad spectrum, difficult to harness but easy to produce. In contrast, laser light is coherent and directional but difficult to create.


Lin’s newly discovered light is sharp and quasi-coherent—and can be produced relatively easily and inexpensively. The discovery is discussed in detail in “Anomalous Thermal Radiation from a Three-Dimensional Optical Photonoic Crystal,” co-authored by Lin and published recently in Nanotechnology.


“It is tremendously exciting when science reveals something new about the fundamental nature of matter, and it is especially gratifying when such a discovery is made by a Rensselaer School of Science faculty member,” said School of Science Dean Curt Breneman. “I am extremely proud of Professor Shawn Lin for identifying a striking new behavior of photonic crystals that could revolutionize the way we think about blackbody radiation—the common effect that explains why hot materials glow red, yellow, or blue-white depending upon their temperature.


"In this groundbreaking work, Professor Lin has revealed that superheated photonic crystals emit much higher intensity radiation than expected, and they do so at a select group of wavelengths in a directional way,” he added. “This is a set of completely new results with potentially wide-ranging implications.”


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For the first time, scientists "squeeze" light one particle at a time

For the first time, scientists "squeeze" light one particle at a time | Amazing Science | Scoop.it

A team of scientists has successfully measured particles of light being “squeezed”, in an experiment that had been written off in physics textbooks as impossible to observe.


Squeezing is a strange phenomenon of quantum physics. It creates a very specific form of light which is “low-noise” and is potentially useful in technology designed to pick up faint signals, such as the detection of gravitational waves.


The standard approach to squeezing light involves firing an intense laser beam at a material, usually a non-linear crystal, which produces the desired effect.


For more than 30 years, however, a theory has existed about another possible technique. This involves exciting a single atom with just a tiny amount of light. The theory states that the light scattered by this atom should, similarly, be squeezed.


Unfortunately, although the mathematical basis for this method – known as squeezing of resonance fluorescence – was drawn up in 1981, the experiment to observe it was so difficult that one established quantum physics textbook despairingly concludes: “It seems hopeless to measure it”.


So it has proven – until now. In the journal Nature, a team of physicists report that they have successfully demonstrated the squeezing of individual light particles, or photons, using an artificially constructed atom, known as a semiconductor quantum dot. Thanks to the enhanced optical properties of this system and the technique used to make the measurements, they were able to observe the light as it was scattered, and proved that it had indeed been squeezed.


Professor Mete Atature, from the Cavendish Laboratory, Department of Physics, and a Fellow of St John’s College at the University of Cambridge, led the research. He said: “It’s one of those cases of a fundamental question that theorists came up with, but which, after years of trying, people basically concluded it is impossible to see for real – if it’s there at all.”


“We managed to do it because we now have artificial atoms with optical properties that are superior to natural atoms. That meant we were able to reach the necessary conditions to observe this fundamental property of photons and prove that this odd phenomenon of squeezing really exists at the level of a single photon. It’s a very bizarre effect that goes completely against our senses and expectations about what photons should do.”

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Photonic heating and cooling with light leads to ultrafast PCR-based DNA diagnostics

Photonic heating and cooling with light leads to ultrafast PCR-based DNA diagnostics | Amazing Science | Scoop.it

A new technology developed by UC Berkeley bioengineers promises to make a workhorse lab tool cheaper, more portable and many times faster by accelerating the heating and cooling of genetic samples with the switch of a light. This turbocharged thermal cycling, described in a paper published July 31 in the journal Light: Science & Application, greatly expands the clinical and research applications of the polymerase chain reaction (PCR) test, with results ready in minutes instead of an hour or more.


The PCR test, which amplifies a single copy of a DNA sequence to produce thousands to millions of copies, has become vital in genomics applications, ranging from cloning research to forensic analysis to paternity tests. PCR is used in the early diagnosis of hereditary and infectious diseases, and for analysis of ancient DNA samples of mummies and mammoths.


Using light-emitting diodes, or LEDs, the UC Berkeley researchers were able to heat electrons at the interface of thin films of gold and a DNA solution. They clocked the speed of heating the solution at around 55 degrees Fahrenheit per second. The rate of cooling was equally impressive, coming in at about 43.9 degrees per second.


“PCR is powerful, and it is widely used in many fields, but existing PCR systems are relatively slow,” said study senior author Luke Lee, a professor of bioengineering. “It is usually done in a lab because the conventional heater used for this test requires a lot of power and is expensive. Because it takes an hour or longer to complete each test, it is not practical for use for point-of-care diagnostics. Our system can generate results within minutes.”


To pick up the pace of this thermal cycling, Lee and his team of researchers took advantage of plasmonics, or the interaction between light and free electrons on a metal’s surface. When exposed to light, the free electrons get excited and begin to oscillate, generating heat. Once the light is off, the oscillations and the heating stop.


Gold, it turns out, is a popular metal for this plasmonic photothermal heating because it is so efficient at absorbing light. It has the added benefit of being inert to biological systems, so it can be used in biomedical applications.


For their experiments, the researchers used thin films of gold that were 120 nanometers thick, or about the width of a rabies virus. The gold was deposited onto a plastic chip with microfluidic wells to hold the PCR mixture with the DNA sample.


The light source was an array of off-the-shelf LEDs positioned beneath the PCR wells. The peak wavelength of the blue LED light was 450 nanometers, tuned to get the most efficient light-to-heat conversion. The researchers were able to cycle from 131 degrees to 203 degrees Fahrenheit 30 times in less than five minutes.


They tested the ability of the photonic PCR system to amplify a sample of DNA, and found that the results compared well with conventional PCR tests. “This photonic PCR system is fast, sensitive and low-cost,” said Lee, who is also co-director of the Berkeley Sensor and Actuator Center. “It can be integrated into an ultrafast genomic diagnostic chip, which we are developing for practical use in the field. Because this technology yields point-of-care results, we can use this in a wide range of settings, from rural Africa to a hospital ER.”


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First color-tunable and first graphene-based LED developed

First color-tunable and first graphene-based LED developed | Amazing Science | Scoop.it

Currently, all light-emitting diodes (LEDs) emit light of only one color, which is predefined during fabrication. So far, tuning the color of light produced by a single LED has never been realized, despite numerous attempts.


So it's quite remarkable that in a new study, scientists have demonstrated an LED that not only can be tuned to emit different colors of light, but can do so across nearly the entire visible spectrum: from blue (450-nm wavelength) to red (750-nm wavelength)—basically all colors but the darkest blues and violets.


The key to achieving the color-tunable LED is making it out of graphene—the same material that has led to groundbreaking research in a number of areas, from batteries to solar cells to semiconductors. Despite graphene's success in these areas, graphene-based LEDs have never been realized before now, making the new device the first-ever graphene-based LED in addition to being the first color-tunable LED.


Applications of the new LED include high-quality, color-tunable LED displays for TVs and mobile devices, color-tunable LED light fixtures, and the potential for a variety of future graphene-based photonic devices.


The researchers, led by Professor Tian-Ling Ren at Tsinghua University in Beijing, made the light-emitting material from the interface of two different forms of graphene. These forms are graphene oxide (GO), which is produced from inexpensive graphite, and reduced graphene oxide (rGO), which is a more pristine form of GO.


Lying at the interface of the GO and rGO is a special type of partially reduced GO that has optical, physical, and chemical properties that lie somewhere in between those of GO and rGO. The most important "blended" property of the interfacial layer is that it has a series of discrete energy levels, which ultimately allows for the emission of light at many different energies, or colors.


The occurrence of this property is especially interesting because, on their own, neither GO nor rGO (or any other known form of graphene, for that matter) can emit any light at all. This is because neither material has the right size "bandgap," which is the gap between two energy bands that electrons must jump across to conduct electricity or emit light. While GO has an extremely large bandgap, rGO has a zero bandgap.


Instead of having a bandgap somewhere in between GO and rGO, the partially reduced interfacial GO actually has many different intermediate bandgaps as a result of how the blending occurs—not as a smooth transition, but in the form of rGO nanoclusters embedded within the GO layer. Because these rGO nanoclusters are reduced to varying degrees at the interface, they exhibit variations in their energy levels and, consequently, in the color of emitted light. These energy levels can be easily modulated by changing the applied voltage or by chemical doping, which selectively stimulates a single color of luminescence and enables tuning of the LED's color.


"We found that a combination of GO and rGO can create a conductive and wide bandgap material," Ren told Phys.org. "It is commonly known that graphene does not have a bandgap. Therefore we were all surprised that our GO/rGO interface (a graphene-based system) can actually be luminescent."

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Nanoscale device that can emit light as powerfully as an object 10,000 times its size

Nanoscale device that can emit light as powerfully as an object 10,000 times its size | Amazing Science | Scoop.it
University of Wisconsin-Madison engineers have created a nanoscale device that can emit light as powerfully as an object 10,000 times its size. It's an advance that could have huge implications for a variety of imaging and energy applications.


In a paper published July 10, 2015 in the journal Physical Review Letters, Zongfu Yu, an assistant professor of electrical and computer engineering at UW-Madison, and his collaborators describe nanoscale device that  that drastically outpaces previous technology in its ability to scatter light.  They showed how a single nanoresonator can manipulate light to cast a very large "reflection."  The nanoresonator's capacity to absorb and emit light energy is such that it can make itself—and, in applications, other very small things—appear 10,000 times as large as its physical size.


"Making an object look much 10,000 times larger than its physical size has lots of implications in technologies related to light," Yu says. The researchers realized the advance through materials innovation and a keen understanding of the physics of light. Much like sound, light can resonate, amplifying itself as the surrounding environment manipulates the physical properties of its wave energy. The researchers took advantage of this by creating an artificial material in which the wavelength of light is much larger than in a vacuum, which allows light waves to resonate more powerfully.


In a paper published July 10, 2015 in the journal Physical Review Letters, Zongfu Yu, an assistant professor of electrical and computer engineering at UW-Madison, and his collaborators describe nanoscale device that  that drastically outpaces previous technology in its ability to scatter light.  They showed how a single nanoresonator can manipulate light to cast a very large "reflection."


The nanoresonator's capacity to absorb and emit light energy is such that it can make itself—and, in applications, other very small things—appear 10,000 times as large as its physical size.


"Making an object look much 10,000 times larger than its physical size has lots of implications in technologies related to light," Yu says. The researchers realized the advance through materials innovation and a keen understanding of the physics of light. Much like sound, light can resonate, amplifying itself as the surrounding environment manipulates the physical properties of its wave energy. The researchers took advantage of this by creating an artificial material in which the wavelength of light is much larger than in a vacuum, which allows light waves to resonate more powerfully.

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Fairy Lights in Femtoseconds: Scientists have created a hologram that can be touched

Fairy Lights in Femtoseconds: Scientists have created a hologram that can be touched | Amazing Science | Scoop.it
Hologram technology already exists. Whatever is not yet sufficiently advanced, however, we have witnessed some progress in this area as: hologram created in mid air by laser, 3D hologram displays, holograms in the toy industry and the like. Unfortunately Hologram display can not be touched and interaction with it would feel more natural.

That at least was true till now when a Japanese team of scientists from Digital Nature Group managed to create a hologram display that you can touch. The concept is similar to the hologram which was created in mid air (also in Japan). Namely, the laser is used to create display emits superfast and supershort radiation (measured in femtoseconds). These radiations wiggle molecules of air, while helping to ionize (resulting in their lighting). As we know, a set of ionized particles to a place called plasma, which is generated by the laser.


The very fact that the molecules are forced to move in the air is causing the ability to touch them. Namely, when you put a finger in the hologram air, molecules are hitting your skin and you feel like it you touched something. According to lead author of the study it feels like you're touching sand paper or electrostatic shock. Additionally, by using a camera which is placed under the display you can recognize when you touched the display and where, and to convey the command somewhere in the software. 


Scientists say that they have chosen femtosecond display nanoseconds because it is safer for the skin because there is not enough time to warm up and damage. This will allow interactive 3D holograms that can be touched, which will contribute to significant progress in hologram technology. The projection of such holograms may allow upgrading of our reality in the case if these kind of devices are placed all around us and project images and objects that we could touch.


This femtosecond laser-based volumetric display will be demonstrated to the public as a part of the Siggraph 2015 exhibition in August.

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Two-beam super-resolution lithography to make 3D photonic 'gyroid' nanostructures

Two-beam super-resolution lithography to make 3D photonic 'gyroid' nanostructures | Amazing Science | Scoop.it

"A team of researchers with Swinburne University of Technology in Australia has found a way to use two-beam super-resolution lithography to create 3D photonic "gyroid" nanostructures—similar to those found in butterfly wings. In their paper published in the journal Science Advances, the team describes their technique and some applications to which it might be applied.


Scientists have known for some time that butterfly wings have "gyroid" nanostructures in them (arranged in grid patterns), that serve the butterflies by manipulating light in useful ways. In addition to their photonic properties, the structures, which are made of intertwining curved surfaces, were also found to be very strong for their size, which has caused scientists to see if they might find a way to create them artificially. Up till now, such efforts have left a lot to be desired—most do not have a high enough resolution or are too fragile. In this new effort, the researchers report that rather than rely on traditional methods, such as two-photon polymerization, the team went with optical two-beam super-resolution lithography—they compare it to direct laser writing techniques, noting that it has two major advantages over other techniques used in the past. The first is that it offers much better resolution and the second is that the resulting structure has more mechanical strength."


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How to twist light into a Möbius strip

How to twist light into a Möbius strip | Amazing Science | Scoop.it
Topological curiosity created from laser beam

 

Möbius strips can easily be made at home – just take a strip of paper, give it a half-twist and then join its ends together. Trivial as it may sound, this loop possesses the unusual property of having only one surface and one edge. They also appear very rarely in nature and had never before been seen in light. Now, an international group of physicists has created such shapes using the polarization of laser light, and the researchers say that these electromagnetic patterns could be used to build new kinds of small-scale structure such as metamaterials.

 

The possibility of making an optical Möbius strip was suggested in 2005 by Isaac Freund of Bar-Ilan University in Israel. Freund calculated that a pair of laser beams could be manipulated such that the axis along which their combined electric fields oscillates – the polarization vector – would trace out a Möbius strip. He proposed using beams with different spin and orbital angular momenta, and making them interfere at specific angles to one another. The spin – or circular polarization – of an electromagnetic wave involves its polarization rotating clockwise or anticlockwise in a circle that is normal to the direction of propagation. Orbital angular momentum, on the other hand, comes from the twisting of a beam's wavefront around its propagation axis.

 

Normally, a light wave vibrates in a plane at right angles to its direction of travel; but crucial to creating a 3D optical pattern such as a Möbius strip is to ensure that it also has a longitudinal component along the propagation axis. It turns out that Freund's proposal for creating this longitudinal component is extremely challenging from an experimental point of view, so in this latest work Peter Banzer of the Max Planck Institute for the Science of Light in Erlangen and colleagues in Germany, Canada, Italy and the US have taken a different approach.

 

Banzer and colleagues used a liquid-crystal device known as a q-plate. When exposed to a beam with a certain spin, a q-plate transforms that beam so that it has opposite spin and 2q units of orbital angular momentum, where q can be any half-integer value and is a property of the particular plate used. The team used a green laser beam that was a superposition of two waves with opposing spin. The result was a beam with a polarization that varied across its width. It was circularly polarized at its centre, but linearly polarized – and with varying orientations of the polarization vector – further out.

 

To extend this 2D pattern of polarizations into the third dimension, the researchers sent the beam through a tight-focusing microscope lens. This gave the beam a longitudinal component – the size of which depended on the degree of focusing. The result was a Möbius strip of polarization that measured just 200–250 nm across. By changing the q-plate, the researchers were able to create Möbius strips with three (q = –1/2) and five half turns (q = –3/2). "It was a puzzle in the community as to whether such a topology could exist physically or whether it was just a mathematical description," says group member Ebrahim Karimi of the University of Ottawa. "But now we have seen this in the lab, we know that Freund's theory is correct."

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Characterizing quantum Hall light zooming around a photonic chip

Characterizing quantum Hall light zooming around a photonic chip | Amazing Science | Scoop.it

The quantum Hall effect is best understood by peering through the lens of topology. In the 1980s, physicists discovered that electrons in some materials behave strangely when subjected to large magnetic fields at extreme cryogenic temperatures. Remarkably, the electrons at the boundary of the material will flow along avenues of travel called ‘edge states’, protected against defects that are most certainly present in the material. Moreover, the conductance--a measure of the current--is quantized. This means that when the magnetic field is ramped up, then the conductance does not change smoothly. Instead it stays flat, like a plateau, and then suddenly jumps to a new value. The plateaus occur at precise values that are independent of many of the material’s properties. This hopping behavior is a form of precise quantization and is what gives the quantum Hall effect its great utility, allowing it to provide the modern standard for calibrating resistance in electronics, for instance.

 

Researchers have engineered quantum Hall behavior in other platforms besides the solid-state realm in which it was originally discovered. Signatures of such physics have been spotted in ultracold atomic gases and photonics, where light travels in fabricated chips. Hafezi and colleagues have led the charge in the photonics field.

 

The group uses a silicon-based chip that is filled with an array of ring-shaped structures called resonators. The resonators are connected to each other via waveguides (figure). The chip design strictly determines the conditions under which light can travel along the edges rather than through the inner regions. The researchers measure the transmission spectrum, which is the fraction of light that successfully passes through an edge pathway. To circulate unimpeded through the protected edge modes, the light must possess a certain energy. The transmission increases when the light energy matches this criteria. For other parameters, the light will permeate the chip interior or get lost, causing the transmission signal to decrease. The compiled transmission spectrum looks like a set of bright stripes separated by darker regions (see figure). Using such a chip, this group previously collected images of light traveling in edge states, definitively demonstrating the quantum Hall physics for photons.

 

In this new experiment Hafezi’s team modified their design to directly measure the value of the topology-related property that characterizes the photonic edge states. This measurement is analogous to characterizing the quantized conductance, which was critical to understanding the electron quantum Hall effect. In photonics, however, conductance is not relevant as it pertains to electron-like behavior. Here the significant feature is the winding number, which is related to how light circulates around the chip. Its value equals to the number of available edge states and should not change in the face of certain disruptions.

 

To extract the winding number, the team adds 100 nanometer titanium heaters on a layer above the waveguides. Heat changes the index of refraction, namely how the light bends as it passes through the waveguides. In this manner, researchers can controllably imprint a phase shift onto the light. Phase can be thought of in terms of a time delay. For instance, when comparing two light waves, the intensity can be the same, but one wave may be shifted in time compared to the other. The two waves overlap when one wave is delayed by a full oscillation cycle—this is called a 2π phase shift.

 

On the chip, enough heat is added to add a 2π phase shift to the light. The researchers observe an energy shift in the transmission stripes corresponding to light traveling along the edge. Notably, in this chip design, the light can circulate either clockwise (CW) or counterclockwise (CCW), and the two travel pathways do not behave the same (in contrast to an interferometer). When the phase shift is introduced, the CW traveling light hops one direction in the transmission spectrum, and the CCW goes the opposite way. The winding number is the amount that these edge-state spectral features move and is exactly equivalent to the quantized jumps in the electronic conductance.

 

Sunil Mittal, lead author and postdoctoral researcher explains one future direction, “So far, our research has been focused on transporting classical [non-quantum] properties of light--mainly the power transmission. It is intriguing to further investigate if this topological system can also achieve robust transport of quantum information, which will have potential applications for on-chip quantum information processing.” 

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Building 'invisible' materials with light

Building 'invisible' materials with light | Amazing Science | Scoop.it

A new method of building materials using light, developed by researchers at the University of Cambridge, could one day enable technologies that are often considered the realm of science fiction, such as invisibility cloaks and cloaking devices.


Although cloaked starships won't be a reality for quite some time, the technique which researchers have developed for constructing materials with building blocks a few billionths of a meter across can be used to control the way that light flies through them, and works on large chunks all at once. Details are published today (28 July, 2015) in the journal Nature Communications.


The key to any sort of 'invisibility' effect lies in the way light interacts with a material. When light hits a surface, it is either absorbed or reflected, which is what enables us to see objects. However, by engineering materials at the nanoscale, it is possible to produce 'metamaterials': materials which can control the way in which light interacts with them. Light reflected by a metamaterial is refracted in the 'wrong' way, potentially rendering objects invisible, or making them appear as something else.


Metamaterials have a wide range of potential applications, including sensing and improving military stealth technology. However, before cloaking devices can become reality on a larger scale, researchers must determine how to make the right materials at the nanoscale, and using light is now shown to be an enormous help in such nano-construction.


The technique developed by the Cambridge team involves using unfocused laser light as billions of needles, stitching gold nanoparticles together into long strings, directly in water for the first time. These strings can then be stacked into layers one on top of the other, similar to Lego bricks. The method makes it possible to produce materials in much higher quantities than can be made through current techniques.


In order to make the strings, the researchers first used barrel-shaped molecules called cucurbiturils (CBs). The CBs act like miniature spacers, enabling a very high degree of control over the spacing between the nanoparticles, locking them in place.


In order to connect them electrically, the researchers needed to build a bridge between the nanoparticles. Conventional welding techniques would not be effective, as they cause the particles to melt. "It's about finding a way to control that bridge between the nanoparticles," said Dr Ventsislav Valev of the University's Cavendish Laboratory, one of the authors of the paper. "Joining a few nanoparticles together is fine, but scaling that up is challenging."


The key to controlling the bridges lies in the cucurbiturils: the precise spacing between the nanoparticles allows much more control over the process. When the laser is focused on the strings of particles in their CB scaffolds, it produces plasmons: ripples of electrons at the surfaces of conducting metals. These skipping electrons concentrate the light energy on atoms at the surface and join them to form bridges between the nanoparticles. Using ultrafast lasers results in billions of these bridges forming in rapid succession, threading the nanoparticles into long strings, which can be monitored in real time.


"We have controlled the dimensions in a way that hasn't been possible before," said Dr Valev, who worked with researchers from the Department of Chemistry and the Department of Materials Science & Metallurgy on the project. "This level of control opens up a wide range of potential practical applications."


Via Anne Pascucci, MPA, CRA, Mark E. Deschaine, PhD, Jocelyn Stoller
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The world's fastest nanoscale photonics switch

The world's fastest nanoscale photonics switch | Amazing Science | Scoop.it
An international team of researchers from Lomonosov Moscow State University and the Australian National University in Canberra created an ultrafast all-optical switch on silicon nanostructures. This device may become a platform for future computers and permit to transfer data at an ultra-high speed. An article with the description of the device was published in the Nano Letters journal and highlighted in Nature Materials.


Three years ago, several groups of researchers simultaneously discovered an important effect: They found out that silicon nanoparticles exhibit strong resonances in the visible spectrum—the so-called magnetic dipole resonances. This type of resonance is characterized by strong localization of light waves on subwavelength scales, inside the nanoparticles. This effect turned out to be interesting to research, but, according to Maxim Shcherbakov, the first author of the article published in Nano Letters, nobody thought that this discovery could lead to the development of a compact and very rapid photonic switch.


Nanoparticles were fabricated in the Australian National University by e-beam lithography followed by plasma-phase etching. It was done by Alexander Shorokhov, who served an internship in the University as a part of Presidential scholarship for studying abroad. The samples were brought to Moscow, and all the experimental work was carried out at the Faculty of Physics of Lomonosov Moscow State University, in the Laboratory of Nanophotonics and Metamaterials.


"In our experimental research, me and my colleague, Polina Vabishchevich from the faculty, used a set of nonlinear optics methods that address femtosecond light matter," explains Maxim Shcherbakov. "We used our femtosecond laser complex, acquired as part of the MSU development program".


Eventually, researchers developed a device: a disc 250 nm in diameter that is capable of switching optical pulses at femtosecond rates (femtosecond is a one millionth of one billionth of a second). Switching speeds that fast enable data transmission and processing devices that will work at tens and hundreds terabits per second. This can make possible downloading thousands of HD movies in less than a second.

The operation of the all-optical switch created by MSU researchers is based on the interaction between two femtosecond pulses. The interaction results from the magnetic resonance of the silicon nanostructures. If the pulses arrive at the nanostructure simultaneously, one of them interacts with the other and dampens it due to the effect of two-photon absorption. If there is a 100-fs delay between the two pulses, the interaction does not occur, and the second pulse goes through the nanostructure without changing.


"We were able to develop a structure with the undesirable free-carrier effects are suppressed," says Maxim Shcherbakov. "Free carriers (electrons and electron holes) place serious restrictions on the speed of signal conversion in the traditional integrated photonics. Our work represents an important step towards novel and efficient active photonic devices— transistors, logic units, and others. Features of the technology implemented in our work will allow its use in silicon photonics. In the near future, we are going to test such nanoparticles in integrated circuits".

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Ultrafast Lasers Offer 3-D Micropatterning of Biocompatible Silk Hydrogels

Ultrafast Lasers Offer 3-D Micropatterning of Biocompatible Silk Hydrogels | Amazing Science | Scoop.it
Tufts University biomedical engineers are using low-energy, ultrafast laser technology to make high-resolution, 3-D structures in silk protein hydrogels. The laser-based micropatterning represents a new approach to customized engineering of tissue and biomedical implants.

The work is reported in a paper in PNAS Early Edition published September 15 online before print: "Laser-based three-dimensional multiscale micropatterning of biocompatible hydrogels for customized tissue engineering scaffolds."

Artificial tissue growth requires pores, or voids, to bring oxygen and nutrients to rapidly proliferating cells in the tissue scaffold.  Current patterning techniques allow for the production of random, micron-scale pores and the creation of channels that are hundreds of microns in diameter, but there is little in between.

The Tufts researchers used an ultrafast, femtosecond laser to generate scalable, high-resolution 3-D voids within silk protein hydrogel, a soft, transparent biomaterial that supports cell growth and allows cells to penetrate deep within it.  The researchers were able to create voids at multiple scales as small as 10 microns and as large at 400 microns over a large volume. 

Further, the exceptional clarity of the transparent silk gels enabled the laser's photons to be absorbed nearly 1 cm below the surface of the gel – more than 10 times deeper than with other materials, without damaging adjacent material. 

The laser treatment can be done while keeping the cell culture sealed and sterile. Unlike most 3-D printing, this technique does not require photoinitiators, compounds that promote photoreactivity but are typically bio-incompatible.  

"Because the femtosecond laser pulses allow us to target specific regions without any damage to the immediate surroundings, we can imagine using such micropatterning to controllably design around living cells, guide cell growth and create an artificial vasculature within an already densely seeded silk hydrogel," said senior author Fiorenzo G. Omenetto, Ph.D. Omenetto is associate dean for research, professor of biomedical engineering and Frank C. Doble professor at Tufts School of Engineering and also holds an appointment in physics in the School of Arts and Sciences.
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New Type of Light Source Emits Single-Photon

New Type of Light Source Emits Single-Photon | Amazing Science | Scoop.it
With the help of a semiconductor quantum dot, physicists at the University of Basel have developed a new type of light source that emits single photons. For the first time, the researchers have managed to create a stream of identical photons from a semiconductor. They have reported their findings in the scientific journal Nature Communications together with colleagues from the University of Bochum.


A single-photon source never emits two or more photons at the same time. Single photons are important in the field of quantum information technology where, for example, they are used in quantum computers. Alongside the brightness and robustness of the light source, the indistinguishability of the photons is especially crucial. In particular, this means that all photons must be precisely the same color. Creating such a source of identical single photons has proven very difficult in the past.


However, quantum dots made of semiconductor materials are offering new hope. A quantum dot consists of a few hundred thousand atoms and forms by self-assembly under certain conditions in a semiconductor. Single electrons can be trapped inside a quantum dot and are confined on a nanometer scale. An individual photon is emitted when a quantum state decays.


A team of scientists led by Dr. Andreas Kuhlmann and Prof. Richard J. Warburton from the University of Basel have already shown in past publications that the indistinguishability of the photons is reduced by the fluctuating nuclear spins of the quantum dot atoms. For the first time ever, the scientists have managed to control the nuclear spins to such an extent that even photons sent out widely separated in time are the same color.


Quantum cryptography and quantum communication are two potential areas of application for single-photon sources. These technologies could make it possible to perform calculations that are far beyond the capabilities of today's computers.

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New, Ultrathin Optical Devices Shape Light in Exotic Ways

New, Ultrathin Optical Devices Shape Light in Exotic Ways | Amazing Science | Scoop.it
Caltech engineers have created flat devices capable of manipulating light in ways that are very difficult or impossible to achieve with conventional optical components.

The new devices are not made of glass, but rather of silicon nanopillars that are precisely arranged into a honeycomb pattern to create a "metasurface" that can control the paths and properties of passing light waves.

These metasurface devices, described in a paper published online on August 31, 2015, in the journal Nature Nanotechnology, could lead to ultracompact optical systems such as advanced microscopes, displays, sensors, and cameras that can be mass-produced using the same photolithography techniques used to manufacture computer microchips.

"Currently, optical systems are made one component at a time, and the components are often manually assembled," says Andrei Faraon (BS '04), an assistant professor of applied physics and materials science, and the study's principal investigator. "But this new technology is very similar to the one used to print semiconductor chips onto silicon wafers, so you could conceivably manufacture millions of systems such as microscopes or cameras at a time."

Seen under a scanning electron microscope, the new metasurfaces that the team created resemble a cut forest where only the stumps remain. Each silicon stump, or pillar, has an elliptical cross section, and by carefully varying the diameters of each pillar and rotating them around their axes, the scientists were able to simultaneously manipulate the phase and polarization of passing light. Light is an electromagnetic field, and the field of single-color, or monochromatic, light oscillates at all points in space with the same frequency but varying relative delays, or phases.
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DIY photonics: Optical chip allows for reprogramming quantum computer in seconds

DIY photonics: Optical chip allows for reprogramming quantum computer in seconds | Amazing Science | Scoop.it

Linear optics processor (credit: University of Bristol) - A fully reprogrammable optical chip that can process photons in quantum computers in an infinite small amount of time.


A fully reprogrammable optical chip that can process photons in quantum computers in an infinite number of ways have been developed by researchers from the University of Bristol in the UK and Nippon Telegraph and Telephone (NTT) in Japan.


The universal “linear optics processor” (LPU) chip is a major step forward in creating a quantum computer to solve problems such as designing new drugs, superfast database searches, and performing otherwise intractable mathematics that aren’t possible for supercomputers — marking a new era of research for quantum scientists and engineers at the cutting edge of quantum technologies, the researchers say.


The chip solves a major barrier in testing new theories for quantum science and quantum computing: the time and resources needed to build new experiments, which are typically extremely demanding due to the notoriously fragile nature of quantum systems.


“A whole field of research has essentially been put onto a single optical chip that is easily controlled,” said University of Bristol research associate Anthony Laing, PhD, project leader and senior author of a paper on the research in the journal Science today (August 14, 2015).


“The implications of the work go beyond the huge resource savings. Now anybody can run their own experiments with photons, much like they operate any other piece of software on a computer. They no longer need to convince a physicist to devote many months of their life to painstakingly build and conduct a new experiment.”


The team demonstrated that by reprogramming it to rapidly perform a number of different experiments, each of which would previously have taken many months to build.


“Once we wrote the code for each circuit, it took seconds to reprogram the chip, and milliseconds for the chip to switch to the new experiment,” explained Bristol PhD student Jacques Carolan, one of the researchers. “We carried out a year’s worth of experiments in a matter of hours. What we’re really excited about is using these chips to discover new science that we haven’t even thought of yet.”


The University of Bristol’s pioneering Quantum in the Cloud is the first service to make a quantum processor publicly accessible. They plan to add more chips like the LPU to the service “so others can discover the quantum world for themselves.”

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The first 'white laser' can shine light over the full spectrum of visible colors

The first 'white laser' can shine light over the full spectrum of visible colors | Amazing Science | Scoop.it

Scientists and engineers at Arizona State University, in Tempe, have created the first lasers that can shine light over the full spectrum of visible colors. The device’s inventors suggest the laser could find use in video displays, solid-state lighting, and a laser-based version of Wi-Fi.


Although previous research has created red, blue, green and other lasers, each of these lasers usually only emitted one color of light. Creating a monolithic structure capable of emitting red, green, and blue all at once has proven difficult because it requires combining very different semiconductors. Growing such mismatched crystals right next to each other often results in fatal defects throughout each of these materials.


But now scientists say they’ve overcome that problem. The heart of the new device is a sheet only nanometers thick made of a semiconducting alloy of zinc, cadmium, sulfur, and selenium. The sheet is divided into different segments. When excited with a pulse of light, the segments rich in cadmium and selenium gave off red light; those rich in cadmium and sulfur emitted green light; and those rich in zinc and sulfur glowed blue.


The researchers grew this alloy in stages, carefully varying the temperature and other growth conditions over time. By controlling the interplay between the vapor, liquid, and solid phases of the different materials that made up this nano-sheet, they ensured that these different crystals could coexist.


The scientists can individually target each segment of the nano-sheet with a light pulse. Varying the power of the light pulses that each section received tuned how intensely they shone, allowing the alser to produce 70 percent more perceptible colors than the most commonly used light sources.


Lasers could be far more energy-efficient than LEDs: While LED-based lighting produces up to about 150 lumens per watt of electricity, lasers could produce more than 400 lumens per watt, says Cun-Zheng Ning, a physicist and electrical engineer at Arizona State University at Tempe who worked on the laser. In addition, he says that white lasers could also lead to video displays with more vivid colors and higher contrast than conventional displays.


Another important potential application could be "Li-Fi", the use of light to connect devices to the Interenet. Li-Fi ould be 10 times faster than today’s Wi-Fi, but "the Li-Fi currently under development is based on LEDs," Ning says. He suggests white-laser based Li-Fi could be 10 to 100 times faster than LED-based Li-Fi, because the lasers can encode data much faster than white LEDs.


In the future, the scientists plan to explore whether they can excite these lasers with electricity instead of with light pulses. They detailed their findingsonline 27 July in the journal Nature Nanotechnology.

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Fluorescent Proteins and the Creation of a Living Laser Inside Living Cells

Fluorescent Proteins and the Creation of a Living Laser Inside Living Cells | Amazing Science | Scoop.it

A few years back, a pair of researchers at Massachusetts General Hospital made human cells glow by impregnating them with a molecule that's normally found in jellyfish called green fluorescent protein (GFP) and packing them into a resonant cavity that amplified the amount of light each cell produced. Now, according to a new study recently published in the journal Nano Letters, a team of scientists from the University of St Andrews have developed a means of making individual glowing cells also act as their own resonant cavities.


The St. Andrews team accomplished this by coaxing each cell to engulf a tiny plastic bubble (the green dot in the image above) that acts as a resonant cavity. Each bubble is precisely sized and imbued with fluorescent dye. When a laser hits the cell, it excites the dye which bounces around and amplifies inside the bubble, then fluoresces at a different wavelength. Interestingly, the color of the light that the cell emits depends on the size of the bubble. So far, the researchers have gotten cells to produce light at three different wavelengths. And while the team has only been able to get the method to work in petri dishes, they hope to further develop it into a means of tracking specific cells -- say, tumor cells -- for days, even weeks.

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Researchers successfully combine two different materials to create new hyper-efficient light-emitting crystal

Researchers successfully combine two different materials to create new hyper-efficient light-emitting crystal | Amazing Science | Scoop.it
It's snack time: you have a plain oatmeal cookie, and a pile of chocolate chips. Both are delicious on their own, but if you can find a way to combine them smoothly, you get the best of both worlds.


Researchers in The Edward S. Rogers Sr. Department of Electrical & Computer Engineering used this insight to invent something totally new: they've combined two promising solar cell materials together for the first time, creating a new platform for LED technology.


The team designed a way to embed strongly luminescent nanoparticles called colloidal quantum dots (the chocolate chips) into perovskite (the oatmeal cookie). Perovskites are a family of materials that can be easily manufactured from solution, and that allow electrons to move swiftly through them with minimal loss or capture by defects.


The work is published in the international journal Nature on July 15, 2015.

"It's a pretty novel idea to blend together these two optoelectronic materials, both of which are gaining a lot of traction," says Xiwen Gong, one of the study's lead authors and a PhD candidate working with Professor Ted Sargent. "We wanted to take advantage of the benefits of both by combining them seamlessly in a solid-state matrix."


The result is a black crystal that relies on the perovskite matrix to 'funnel' electrons into the quantum dots, which are extremely efficient at converting electricity to light. Hyper-efficient LED technologies could enable applications from the visible-light LED bulbs in every home, to new displays, to gesture recognition using near-infrared wavelengths.

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