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  • richardmitnick 10:37 am on August 5, 2016 Permalink | Reply
    Tags: , , Light studies   

    From ICL: “Scientists discover light could exist in a previously unknown form” 

    Imperial College London
    Imperial College London

    05 August 2016
    Hayley Dunning

    Artistic image of light trapped on the surface of a nanoparticle topological insulator. No image credit.

    New research suggests that it is possible to create a new form of light by binding light to a single electron, combining the properties of both.

    According to the scientists behind the study, from Imperial College London, the coupled light and electron would have properties that could lead to circuits that work with packages of light – photons – instead of electrons.

    It would also allow researchers to study quantum physical phenomena, which govern particles smaller than atoms, on a visible scale.

    In normal materials, light interacts with a whole host of electrons present on the surface and within the material. But by using theoretical physics to model the behaviour of light and a recently-discovered class of materials known as topological insulators, Imperial researchers have found that it could interact with just one electron on the surface.

    This would create a coupling that merges some of the properties of the light and the electron. Normally, light travels in a straight line, but when bound to the electron it would instead follow its path, tracing the surface of the material.

    Improved electronics

    In the study, published today in Nature Communications, Dr Vincenzo Giannini and colleagues modelled this interaction around a nanoparticle – a small sphere below 0.00000001 metres in diameter – made of a topological insulator.

    Their models showed that as well as the light taking the property of the electron and circulating the particle, the electron would also take on some of the properties of the light.

    Normally, as electrons are travelling along materials, such as electrical circuits, they will stop when faced with a defect. However, Dr Giannini’s team discovered that even if there were imperfections in the surface of the nanoparticle, the electron would still be able to travel onwards with the aid of the light.

    If this could be adapted into photonic circuits, they would be more robust and less vulnerable to disruption and physical imperfections.

    Quantum experiments

    Dr Giannini said: “The results of this research will have a huge impact on the way we conceive light. Topological insulators were only discovered in the last decade, but are already providing us with new phenomena to study and new ways to explore important concepts in physics.”

    Dr Giannini added that it should be possible to observe the phenomena he has modelled in experiments using current technology, and the team is working with experimental physicists to make this a reality.

    He believes that the process that leads to the creation of this new form of light could be scaled up so that the phenomena could observed much more easily.

    Currently, quantum phenomena can only be seen when looking at very small objects or objects that have been super-cooled, but this could allow scientists to study these kinds of behaviour at room temperature.

    See the full article here .

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    Imperial College London

    Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

  • richardmitnick 6:55 am on July 25, 2016 Permalink | Reply
    Tags: , , Light studies   

    From COSMOS: “What shape are photons? Quantum holography sheds light” 

    Cosmos Magazine bloc


    20 July 2016
    Cathal O’Connell

    Hologram of a single photon reconstructed from raw measurements (left) and theoretically predicted (right). Credit FUW

    Imagine a shaft of yellow sunlight beaming through a window. Quantum physics tells us that beam is made of zillions of tiny packets of light, called photons, streaming through the air. But what does an individual photon “look” like? Does it have a shape? Are these questions even meaningful?

    Now, Polish physicists have created the first ever hologram of a single light particle. The feat, achieved by observing the interference of two intersecting light beams, is an important insight into the fundamental quantum nature of light.

    The result could also be important for technologies that require an understanding of the shape of single photons – such as quantum communication and quantum computers.

    ”We performed a relatively simple experiment to measure and view something incredibly difficult to observe: the shape of wavefronts of a single photon,” says Radoslaw Chrapkiewicz, a physicist at the University of Warsaw and lead author of the new paper, published in Nature Photonics.

    For hundreds of years, physicists have been working to figure out what light is made of. In the 19th century, the debate seemed to be settled by Scottish physicist James Clerk Maxwell’s description of light as a wave of electromagnetism.

    But things got a bit more complicated at the turn of the 20th century when German physicist Max Planck, then fellow countryman Albert Einstein, showed light was made up of tiny indivisible packets called photons.

    In the 1920s, Austrian physicist Erwin Schrödinger elaborated on these ideas with his equation for the quantum wave function to describe what a wave looks like, which has proved incredibly powerful in predicting the results of experiments with photons. But, despite the success of Schrödinger’s theory, physicists still debate what the wave function really means.

    Now physicists at the University of Warsaw measured, for the first time, the shape described by Schrödinger’s equation in a real experiment.

    Photons, travelling as waves, can be in step (called having the same phase). If they interact, they produce a bright signal. If they’re out of phase, they cancel each other out. It’s like sound waves from two speakers producing loud and quiet patches in a room.

    The image – which is called a hologram because it holds information on both the photon’s shape and phase – was created by firing two light beams at a beamsplitter, made of calcite crystal, at the same time.

    The beamsplitter acts a bit like a traffic intersection, where each photon can either pass straight on through or make a turn. The Polish team’s experiment hinged on measuring which path each photon took, which depends on the shape of their wave functions.

    Scheme of the experimental setup for measuring holograms of single photons.Credit FUW / dualcolor.pl / jch

    For a photon on its own, each path is equally probable. But when two photons approach the intersection, they interact – and these odds change.

    The team realised that if they knew the wave function of one of the photons, they could figure out the shape of the second from the positions of flashes appearing on a detector.

    It’s a little like firing two bullets to glance off one another mid-air and using the deflected trajectories to figure our shape of each projectile.

    Each run of the experiment produced two flashes on a detector, one for each photon. After more than 2,000 repetitions, a pattern of flashes built up and the team were able to reconstruct the shape of the unknown photon’s wave function.

    The resulting image looks a bit like a Maltese cross, just like the wave function predicted from Schrödinger’s equation. In the arms of the cross, where the photons were in step, the image is bright – and where they weren’t, we see darkness.

    The experiment brings us “a step closer to understanding what the wave function really is,” says Michal Jachura, who co-authored the work, and it could be a new tool for studying the interaction between two photons, on which technologies such as quantum communication and some versions of quantum computing rely.

    The researchers also hope to recreate wave functions of more complex quantum objects, such as atoms.

    “It’s likely that real applications of quantum holography won’t appear for a few decades yet,” says Konrad Banaszek, who was also part of the team, “but if there’s one thing we can be sure of it’s that they will be surprising.”

    See the full article here .

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  • richardmitnick 9:12 am on June 10, 2016 Permalink | Reply
    Tags: , Light studies, , Researchers demonstrate a 100x increase in the amount of information that can be 'packed into light', University of the Witwatersrand   

    From phys.org: “Researchers demonstrate a 100x increase in the amount of information that can be ‘packed into light’ “ 


    Data of the Rubik’s cube sent and received. Credit: Wits University

    The rise of big data and advances in information technology has serious implications for our ability to deliver sufficient bandwidth to meet the growing demand.

    Researchers at the University of the Witwatersrand in Johannesburg, South Africa, and the Council for Scientific and Industrial Research (CSIR) are looking at alternative sources that will be able to take over where traditional optical communications systems are likely to fail in future.

    In their latest research, published online today (10 June 2016) in the scientific journal, Scientific Reports, the team from South Africa and Tunisia demonstrate over 100 patterns of light used in an optical communication link, potentially increasing the bandwidth of communication systems by 100 times.

    The idea was conceived by Professor Andrew Forbes from Wits University, who led the collaboration. The key experiment was performed by Dr Carmelo Rosales-Guzman, a Research Fellow in the Structured Light group in the Wits School of Physics, and Dr Angela Dudley of the CSIR, an honorary academic at Wits.

    The first experiments on the topic were carried out by Abderrahmen Trichili of Sup’Com (Tunisia) as a visiting student to South Africa as part of an African Laser Centre funded research project. The other team members included Bienvenu Ndagano (Wits), Dr Amine Ben Salem (Sup’Com) and Professor Mourad Zghal (Sup’Com), all of who contributed significantly to the work.

    Bracing for the bandwidth ceiling

    Traditional optical communication systems modulate the amplitude, phase, polarisation, colour and frequency of the light that is transmitted. Yet despite these technologies, we are predicted to reach a bandwidth ceiling in the near future.

    Dr. Carmelo Rosales-Guzman from Wits University. Credit: Wits University

    But light also has a “pattern” – the intensity distribution of the light, that is, how it looks on a camera or a screen.

    Since these patterns are unique, they can be used to encode information:

    pattern 1 = channel 1 or the letter A,
    pattern 2 = channel 2 or the letter B, and so on.

    What does this mean?

    That future bandwidth can be increased by precisely the number of patterns of light we are able to use.

    Ten patterns mean a 10x increase in existing bandwidth, as 10 new channels would emerge for data transfer.

    At the moment modern optical communication systems only use one pattern. This is due to technical hurdles in how to pack information into these patterns of light, and how to get the information back out again.

    How the research was done

    In this latest work [not available until paper is published], the team showed data transmission with over 100 patterns of light, exploiting three degrees of freedom in the process.

    They used digital holograms written to a small liquid crystal display (LCD) and showed that it is possible to have a hologram encoded with over 100 patterns in multiple colours.

    “This is the highest number of patterns created and detected on such a device to date, far exceeding the previous state-of-the-art,” says Forbes.

    One of the novel steps was to make the device ‘colour blind’, so the same holograms can be used to encode many wavelengths.

    According to Rosales-Guzman to make this work “100 holograms were combined into a single, complex hologram. Moreover, each sub-hologram was individually tailored to correct for any optical aberrations due to the colour difference, angular offset and so on”.

    What’s next?

    The next stage is to move out of the laboratory and demonstrate the technology in a real-world system.

    “We are presently working with a commercial entity to test in just such an environment,” says Forbes. The approach of the team could be used in both free-space and optical fibre networks.

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

  • richardmitnick 9:06 pm on February 3, 2016 Permalink | Reply
    Tags: , Light studies, ,   

    From New Scientist: “Shortest ever pulse of visible light spots photons fleeing atoms” 


    New Scientist

    3 February 2016
    Colin Barras

    Light field synthesiser
    Got a light? Christian Hackenberger/Attoelectronics MPQ

    The ultimate high-speed flashbulb just measured how quickly electrons inside atoms respond to light. The work could speed the development of light-based electronics.

    At 380 attoseconds long – 380 x 10-18 seconds – the flashes are the shortest pulses of visible light ever created in the lab.

    Eleftherios Goulielmakis at the Max Planck Institute of Quantum Optics in Garching, Germany, and his colleagues achieved a similar feat in 2008 when they generated pulses of extreme ultraviolet (EUV) light that were just 80 attoseconds long.

    But making such short pulses of visible light is more challenging – and also more useful. EUV is energetic enough to strip electrons away from an atom altogether. Visible light makes a gentler probe: it energises electrons in an atom, encouraging them to emit light of their own, without actually removing them from the atom’s clutches.

    This time, Goulielmakis’s key tool was a light field synthesiser, which carefully combines several light pulses of known wavelengths to generate the incredibly short flashes. Those pulses are brought together with their wavelengths slightly out of phase, so some parts of the combined light cancel each other out and leave a super-short pulse behind (see video, below). The same principle explains why two ocean waves that are perfectly out of sync will destroy each other on contact and leave an apparently calm surface.

    Kicking out a photon

    Theory suggested that electrons take a few hundred attoseconds [1×10^−18 of a second, quintillionth of a second] to kick out a fresh photon after they’ve been hit by an incoming beam, but the precise figure was unknown. The 380-attosecond-long light pulses are ideal for testing this idea. Not only can the pulses energise the electrons, they can then act as a camera flash, illuminating the process just long enough for scientists to measure the time it takes the electrons to respond.

    Goulielmakis and his colleagues aimed their short pulses at gaseous krypton atoms in a vacuum, and found that the electrons in the krypton kicked out UV photons 115 attoseconds later.

    The atoms behaved a bit like an energy-saving light bulb, Goulielmakis says. “Turn on the switch and the lamp is a bit dim – it takes time to get bright,” he says. “An electron in an atom also needs time to respond and maximise its emission of radiation – it needs about 100 attoseconds.”

    “This work indeed represents a major step forward in the control of electrons,” says Peter Hommelhoff at the University of Erlangen-Nuremberg in Germany.

    Overtaking electrons

    Goulielmakis and his colleagues plan to extend the work to examine the way electrons behave in other materials – particularly solids.

    “[This] may lead to important new insights into the dynamics of electrons in a wide class of materials,” says Jon Marangos at Imperial College London. Those insights could help improve the design and efficiency of electronic devices.

    Many people predict that computer circuits will eventually use photons rather than electrons to ferry information, but for that to work, photons have to interact with each other inside physical matter – things like the semiconductors used in today’s computers. So exploring how rapidly semiconductors and other solids respond to incoming light will help determine exactly how fast such light-based electronics will be able to operate. “This is the bridge between photonics and electronics,” says Goulielmakis. “We have to make sure we understand it.”

    Journal reference: Nature, DOI: 10.1038/nature16528

    See the full article here .

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  • richardmitnick 12:55 pm on October 19, 2015 Permalink | Reply
    Tags: , , Light studies, Zero-index material   

    From Harvard: “To infinity and beyond” 

    Harvard University

    Harvard University

    Harvard School of Engineering and Applied Sciences

    October 19, 2015
    Leah Burrows

    New zero-index material made of silicon pillar arrays embedded in a polymer matrix and clad in gold film creates a constant phase of light, which stretches out in infinitely long wavelengths. (Illustration by Credit: Peter Allen/Harvard SEAS)

    Electrons are so 20th century. In the 21st century, photonic devices, which use light to transport large amounts of information quickly, will enhance or even replace the electronic devices that are ubiquitous in our lives today. But there’s a step needed before optical connections can be integrated into telecommunications systems and computers: researchers need to make it easier to manipulate light at the nanoscale.

    Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have done just that, designing the first on-chip metamaterial with a refractive index of zero, meaning that the phase of light can travel infinitely fast.

    This new metamaterial was developed in the lab of Eric Mazur, the Balkanski Professor of Physics and Applied Physics and Area Dean for Applied Physics at SEAS, and is described in the journal Nature Photonics.

    “Light doesn’t typically like to be squeezed or manipulated but this metamaterial permits you to manipulate light from one chip to another, to squeeze, bend, twist and reduce diameter of a beam from the macroscale to the nanoscale,” said Mazur. “It’s a remarkable new way to manipulate light.”

    Although this infinitely high velocity sounds like it breaks the rule of relativity, it doesn’t. Nothing in the universe travels faster than light carrying information — [Albert] Einstein is still right about that. But light has another speed, measured by how fast the crests of a wavelength move, known as phase velocity. This speed of light increases or decreases depending on the material it’s moving through.

    When light passes through water, for example, its phase velocity is reduced as its wavelengths get squished together. Once it exits the water, its phase velocity increases again as its wavelength elongates. How much the crests of a light wave slow down in a material is expressed as a ratio called the refraction index — the higher the index, the more the material interferes with the propagation of the wave crests of light. Water, for example, has a refraction index of about 1.3.

    When the refraction index is reduced to zero, really weird and interesting things start to happen.

    In a zero-index material, there is no phase advance, meaning light no longer behaves as a moving wave, traveling through space in a series of crests and troughs. Instead, the zero-index material creates a constant phase — all crests or all troughs — stretching out in infinitely long wavelengths. The crests and troughs oscillate only as a variable of time, not space.

    This uniform phase allows the light to be stretched or squished, twisted or turned, without losing energy. A zero-index material that fits on a chip could have exciting applications, especially in the world of quantum computing.

    “Integrated photonic circuits are hampered by weak and inefficient optical energy confinement in standard silicon waveguides,” said Yang Li, a postdoctoral fellow in the Mazur Group and first author on the paper. “This zero-index metamaterial offers a solution for the confinement of electromagnetic energy in different waveguide configurations because its high internal phase velocity produces full transmission, regardless of how the material is configured.”

    The metamaterial consists of silicon pillar arrays embedded in a polymer matrix and clad in gold film. It can couple to silicon waveguides to interface with standard integrated photonic components and chips.

    “In quantum optics, the lack of phase advance would allow quantum emitters in a zero-index cavity or waveguide to emit photons which are always in phase with one another,” said Philip Munoz, a graduate student in the Mazur lab and co-author on the paper. “It could also improve entanglement between quantum bits, as incoming waves of light are effectively spread out and infinitely long, enabling even distant particles to be entangled.”

    “This on-chip metamaterial opens the door to exploring the physics of zero index and its applications in integrated optics,” said Mazur.

    See the full article here .

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    Harvard University campus

    Harvard is the oldest institution of higher education in the United States, established in 1636 by vote of the Great and General Court of the Massachusetts Bay Colony. It was named after the College’s first benefactor, the young minister John Harvard of Charlestown, who upon his death in 1638 left his library and half his estate to the institution. A statue of John Harvard stands today in front of University Hall in Harvard Yard, and is perhaps the University’s best known landmark.

    Harvard University has 12 degree-granting Schools in addition to the Radcliffe Institute for Advanced Study. The University has grown from nine students with a single master to an enrollment of more than 20,000 degree candidates including undergraduate, graduate, and professional students. There are more than 360,000 living alumni in the U.S. and over 190 other countries.

  • richardmitnick 1:34 pm on August 31, 2015 Permalink | Reply
    Tags: , Light studies,   

    From phys.org: “Scientists ‘squeeze’ light one particle at a time” 


    August 31, 2015
    No Writer Credit

    An image from an experiment in the quantum optics laboratory in Cambridge. Laser light was used to excite individual tiny, artificially constructed atoms known as quantum dots, to create “squeezed” single photons. Credit: Mete Atature

    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, a Fellow of St John’s College at the University of Cambridge, who led the research, 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.”

    The left diagram represents electromagnetic activity associated with light at its lowest possible level, according to the laws of classical physics. On the right, part of the field has been reduced to lower than is technically possible, at the expense of making another part of the field less measurable. This effect is called “squeezing” because of the shape it produces. Credit: Mete Atature

    It begins with the fact that wherever there are light particles, there are also associated electromagnetic fluctuations. This is a sort of static which scientists refer to as “noise”. Typically, the more intense light gets, the higher the noise. Dim the light, and the noise goes down.

    But strangely, at a very fine quantum level, the picture changes. Even in a situation where there is no light, electromagnetic noise still exists. These are called vacuum fluctuations. While classical physics tells us that in the absence of a light source we will be in perfect darkness, quantum mechanics tells us that there is always some of this ambient fluctuation.

    “If you look at a flat surface, it seems smooth and flat, but we know that if you really zoom in to a super-fine level, it probably isn’t perfectly smooth at all,” Atature said. “The same thing is happening with vacuum fluctuations. Once you get into the quantum world, you start to get this fine print. It looks like there are zero photons present, but actually there is just a tiny bit more than nothing.”

    Importantly, these vacuum fluctuations are always present and provide a base limit to the noise of a light field. Even lasers, the most perfect light source known, carry this level of fluctuating noise.

    This is when things get stranger still, however, because, in the right quantum conditions, that base limit of noise can be lowered even further. This lower-than-nothing, or lower-than-vacuum, state is what physicists call squeezing.

    In the Cambridge experiment, the researchers achieved this by shining a faint laser beam on to their artificial atom, the quantum dot. This excited the quantum dot and led to the emission of a stream of individual photons. Although normally, the noise associated with this photonic activity is greater than a vacuum state, when the dot was only excited weakly the noise associated with the light field actually dropped, becoming less than the supposed baseline of vacuum fluctuations.

    Explaining why this happens involves some highly complex quantum physics. At its core, however, is a rule known as Heisenberg’s uncertainty principle. This states that in any situation in which a particle has two linked properties, only one can be measured and the other must be uncertain.

    In the normal world of classical physics, this rule does not apply. If an object is moving, we can measure both its position and momentum, for example, to understand where it is going and how long it is likely to take getting there. The pair of properties – position and momentum – are linked.

    In the strange world of quantum physics, however, the situation changes. Heisenberg states that only one part of a pair can ever be measured, and the other must remain uncertain.

    In the Cambridge experiment, the researchers used that rule to their advantage, creating a tradeoff between what could be measured, and what could not. By scattering faint laser light from the quantum dot, the noise of part of the electromagnetic field was reduced to an extremely precise and low level, below the standard baseline of vacuum fluctuations. This was done at the expense of making other parts of the electromagnetic field less measurable, meaning that it became possible to create a level of noise that was lower-than-nothing, in keeping with Heisenberg’s uncertainty principle, and hence the laws of quantum physics.

    Plotting the uncertainty with which fluctuations in the electromagnetic field could be measured on a graph creates a shape where the uncertainty of one part has been reduced, while the other has been extended. This creates a squashed-looking, or “squeezed” shape, hence the term, “squeezing” light.

    Atature added that the main point of the study was simply to attempt to see this property of single photons, because it had never been seen before. “It’s just the same as wanting to look at Pluto in more detail or establishing that pentaquarks are out there,” he said. “Neither of those things has an obvious application right now, but the point is knowing more than we did before. We do this because we are curious and want to discover new things. That’s the essence of what science is all about.”

    See the full article here.

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

  • richardmitnick 6:37 am on March 14, 2015 Permalink | Reply
    Tags: , , Light studies   

    From Huff Post: “Light: Going Beyond the Bulb” 

    Huffington Post
    The Huffington Post

    Kimberly K. Arcand
    Visualization Lead, NASA’s Chandra X-ray Observatory
    NASA Chandra Telescope

    In this piece of art, light bulbs were placed in a medical X-ray machine. The artist then added color to the individual light bulbs to create the desired effect. Credit: Dr. Paula Fontaine/http://www.RadiantArtStudios.com

    Light is one of those things that we almost inevitably take for granted. In fact, many of us might not realize the extent that we overlook its contributions to our lives, because it’s hard to see – literally — just how much it does.

    The light that humans can detect with their eyes is but a mere fraction of the total light out there. Light takes many forms, including radio waves, microwaves, infrared, ultraviolet, X-rays and gamma rays.

    The electromagnetic spectrum includes wavelengths and energies from radio to gamma rays. Illustration: NASA/CXC/M.Weiss

    We rely on light — both natural and sources made by humans — to brighten our world. In the form of radio waves and microwaves, light is also used for communication and navigation through cellphones and GPS. Medical tools that use light, including the highest-energy light of X-rays and gamma rays, help us monitor our bodies and attack certain diseases such as cancer.

    We use light for many purposes including some basic ones such as illuminating our way. This image combines eight different photos, each with exposures of 30 seconds, which show car headlights along a highway. In the future, reflected lasers may power more of our headlights, providing a more powerful and energy-efficient (yet still safe) beam that lights our way through the night.

    Scientists use instruments on the ground and in space that detect different types of light like infrared to monitor our climate and forecast our weather. Astronomers capture light in all types from the cosmos to understand distant galaxies, to look for signs of life beyond Earth, and to learn more about our own planet.

    Images taken from satellites in space in different types of light help us better predict weather and understand the science that drives it. Credit: NASA/JSC/Mike Trenchard

    In addition to its pivotal role in various industrial processes, light may very well represent our future for powering the planet. After all, the sunlight contains enormous amounts of energy that, if we could efficiently capture it, it could provide sustainable power for billions of people.

    Solar panels allow us to harness some of the vast energy that is provided to us every day from the Sun. Credit: Dennis Schroeder/NREL

    For these and many other reasons, the United Nations has declared 2015 to be the “International Year of Light.” We’ve put together a collection of spectacular images in an online exhibit called “Light: Beyond the Bulb” to help celebrate light and all of the amazing things it can do. Here is a sampling of facts about the wonders of light:

    Light comes in different forms. The light that we see with our eyes is just a fraction of all light. Light encompasses wavelengths ranging from radio waves to gamma rays in what is called the “electromagnetic spectrum.”

    This object, officially titled Messier 16, is nicknamed the “Pillars of Creation.” This spectacular image from the Hubble Space Telescope captures this region of space where baby stars are forming in ultraviolet and visible light. Credit: NASA, ESA, Hubble Heritage Team (STScI/AURA)

    By combining light from several NASA different telescopes that detect X-ray, infrared, visible, and ultraviolet light, this image reveals information about the galaxy this galaxy could never be gleaned from just one band of light. Credit: X-ray: NASA/CXC/SAO; UV: NASA/JPL-Caltech; Optical: NASA/STScI; IR: NASA/JPL-Caltech

    NASA Spitzer Telescope

    NASA Hubble Telescope
    NASA/ESA Hubble

    Matter being pulled toward a giant black hole usually doesn’t glow in the light we can see with our eyes – rather it is revealed through light as radio waves and X-rays. This image captures the Hercules A galaxy that has an enormous jet blasting away from its black hole.
    Credit: X-ray: NASA/CXC/SAO, Optical: NASA/STScI, Radio: NSF/NRAO/VLA


    Nothing in the Universe can travel faster than light. In a vacuum, light travels at over 300,000 kilometers (186,000 miles) per second. This means light could circle the Earth 7.5 times in one second.

    While moving at 17,000 miles per hour at an altitude of 240 miles above the Earth’s surface on the International Space Station, NASA astronaut Don Petit was able to capture the lights from our planet in a unique way. His time-lapse photographs–taken from this unusual vantage point–feature star trails, terrestrial lights, and auroras. Credit: NASA/JSC

    As light travels, its path can be bent when it goes from one medium to another (such as air to water). It can also be blocked (when a shadow occurs, for example), reflected (as with a mirror), or absorbed (like when a stone is heated by infrared light from the Sun.)

    This rainbow is caused by light being refracted (bent) when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it. This causes the combined colors of sunlight to spread out into the familiar red, orange, yellow, green, blue, indigo, and violet of a rainbow. Credit: Lisa & Jeffrey Smith

    Shadows are a familiar experience for most of us. Any time an object blocks the light from another source, it can form a shadow. In this photograph, we see shadows on the spectacular walls of Antelope Canyon in Arizona as sunlight streams through an opening above. Credit: J L Spaulding, creative commons license

    Reflection consists of two rays: an incoming or ‘incident’ ray and an outgoing or ‘reflected’ ray. All reflected light obeys the rule that says the incident ray strikes a surface at the same angle that the reflected ray bounces away from it. In the case of a smooth surface like a mirror or the calm top of a lake, a clear identical image is produced. Credit: Prabhu B Doss

    Humans have learned how to harness light and employ it in technologies ranging from medical devices to cell phones to giant telescopes.

    The image shown here is from a laser-scanning microscope of a mouse retina, where the cells have been stained with fluorescent dye to show different features. By studying the microscopic structure of both diseased and normal retina and optic nerves through this light-based technique, scientists hope to better understand the biology of these tissues and the prospects of developing therapeutic interventions. Credit: National Institute of General Medical Sciences (NIGMS

    Because of their capacity to carry massive amounts of data in the form of light, optical fibers serve as the backbone of the Internet. Almost every video and photo you download and nearly every email and text you send travels over optical fiber, sometimes across the world. The ability to transport confined light inside bent fibers means that they can also be used in endoscopes for imaging the interiors of both people and machines. Credit: Optoelectronics Research Centre, Southampton, UK

    Lasers are based on controlling the way that energized atoms release photons, or packets of light. Lasers emit light coherently allowing it to be focused to a tight spot up close or over long distances. This image shows one innovative use of lasers. By beaming a laser into the sky, astronomers can measure and then compensate for the blurring effects of the Earth’s atmosphere, allowing for clearer images of distant cosmic objects. Credit: ESO/B. Tafreshi (twanight.org)

    See the full article here.

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  • richardmitnick 7:54 pm on March 2, 2015 Permalink | Reply
    Tags: , , Light studies, ,   

    From EPFL: “The first ever photograph of light as both a particle and wave” 

    EPFL bloc

    Ecole Polytechnique Federale Lausanne


    March 2, 2015

    Light behaves both as a particle and as a wave. Since the days of [Albert] Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at EPFL have succeeded in capturing the first-ever snapshot of this dual behavior.

    Quantum mechanics tells us that light can behave simultaneously as a particle or a wave. However, there has never been an experiment able to capture both natures of light at the same time; the closest we have come is seeing either wave or particle, but always at different times. Taking a radically different experimental approach, EPFL scientists have now been able to take the first ever snapshot of light behaving both as a wave and as a particle. The breakthrough work is published in Nature Communications.

    When UV light hits a metal surface, it causes an emission of electrons. Albert Einstein explained this “photoelectric” effect by proposing that light – thought to only be a wave – is also a stream of particles. Even though a variety of experiments have successfully observed both the particle- and wave-like behaviors of light, they have never been able to observe both at the same time.

    A research team led by Fabrizio Carbone at EPFL has now carried out an experiment with a clever twist: using electrons to image light. The researchers have captured, for the first time ever, a single snapshot of light behaving simultaneously as both a wave and a stream of particles particle.

    The experiment is set up like this: A pulse of laser light is fired at a tiny metallic nanowire. The laser adds energy to the charged particles in the nanowire, causing them to vibrate. Light travels along this tiny wire in two possible directions, like cars on a highway. When waves traveling in opposite directions meet each other they form a new wave that looks like it is standing in place. Here, this standing wave becomes the source of light for the experiment, radiating around the nanowire.

    This is where the experiment’s trick comes in: The scientists shot a stream of electrons close to the nanowire, using them to image the standing wave of light. As the electrons interacted with the confined light on the nanowire, they either sped up or slowed down. Using the ultrafast microscope to image the position where this change in speed occurred, Carbone’s team could now visualize the standing wave, which acts as a fingerprint of the wave-nature of light.

    While this phenomenon shows the wave-like nature of light, it simultaneously demonstrated its particle aspect as well. As the electrons pass close to the standing wave of light, they “hit” the light’s particles, the photons. As mentioned above, this affects their speed, making them move faster or slower. This change in speed appears as an exchange of energy “packets” (quanta) between electrons and photons. The very occurrence of these energy packets shows that the light on the nanowire behaves as a particle.

    “This experiment demonstrates that, for the first time ever, we can film quantum mechanics – and its paradoxical nature – directly,” says Fabrizio Carbone. In addition, the importance of this pioneering work can extend beyond fundamental science and to future technologies. As Carbone explains: “Being able to image and control quantum phenomena at the nanometer scale like this opens up a new route towards quantum computing.”

    This work represents a collaboration between the Laboratory for Ultrafast Microscopy and Electron Scattering of EPFL, the Department of Physics of Trinity College (US) and the Physical and Life Sciences Directorate of the Lawrence Livermore National Laboratory. The imaging was carried out EPFL’s ultrafast energy-filtered transmission electron microscope – one of the two in the world.

    See the full article here.

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    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

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