Adam Norwood

Tag: optics

  • Cryptochrome

    Research continues on whether humans (and other animals) have the ability to perceive magnetic fields:

    Many birds have a compass in their eyes. Their retinas are loaded with a protein called cryptochrome, which is sensitive to the Earth’s magnetic fields. It’s possible that the birds can literally see these fields, overlaid on top of their normal vision. This remarkable sense allows them to keep their bearings when no other landmarks are visible.

    But cryptochrome isn’t unique to birds – it’s an ancient protein with versions in all branches of life. In most cases, these proteins control daily rhythms. Humans, for example, have two cryptochromes – CRY1 and CRY2 – which help to control our body clocks. But Lauren Foley from the University of Massachusetts Medical School has found that CRY2 can double as a magnetic sensor.

    Vision is amazing, even more so when you take into account the myriad other things that animals and insects can detect beyond just our “visible” EMF spectrum. See also: box jellyfish with their surprisingly complex (and human-like) set of 24 eyes.

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  • 26 Terabit-per-second Laser
    Visit the source: www.bbc.co.uk

    Researchers at the Karlsruhe Institute of Technology set a new record by transmitting 26 terabits of a data per second (“the entire Library of Congress in 10 seconds!” as the usual benchmark goes) using a single laser and a clever FFT and frequency comb technique to split the light into 300+ discrete colors:

    The Fourier transform is a well-known mathematical trick that can in essence extract the different colours from an input beam, based solely on the times that the different parts of the beam arrive. The team does this optically – rather than mathematically, which at these data rates would be impossible – by splitting the incoming beam into different paths that arrive at different times, recombining them on a detector. In this way, stringing together all the data in the different colours turns into the simpler problem of organising data that essentially arrive at different times.

    Neat.

    (Via ACM TechNews)

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  • Optical tweezers and laser tractor beams
    Visit the source: blogs.discovermagazine.com

    Mind-boggling stuff like this is why I keep reading science journals. We can already use photons to push and pinch things with their tiny mass (amazing enough), but new research is underway in how to pull with photons:

    Light is pushy. The physical pressure of photons is what allows for solar sail space missions that ride on sunlight, and what allows for dreams of lasers that will push those sails even faster. And light can trap objects, too: Optical tweezers can hold tiny objects in place. Pulling an object with light, however, is another matter.  …  Jun Chen’s research team says that the key is to use not a regular laser beam, but instead what’s called a Bessel beam. Viewed head-on, a Bessel beam looks like one intense point surrounded by concentric circles—what you might see when you toss a stone into a lake.

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  • Physicists break color barrier for sending, receiving photons
    Visit the source: uonews.uoregon.edu

    To be filed under “research I like reading about even if I don’t quite understand how it works”, new studies from the University of Oregon into altering and controlling the color of light on the scale of individual photons in fiber optic signalling:

    In experiments led by Raymer’s doctoral student Hayden J. McGuinness, researchers used two lasers to create an intense burst of dual-color light, which when focused into the same optical fiber carrying a single photon of a distinct color causes that photon to change to a new color. This occurs through a process known as Bragg scattering, whereby a small amount of energy is exchanged between the laser light and the single photon, causing its color to change. […] 

    “In the first study, we worked with one photon at a time with two laser bursts to change the energy and color without using hydrogen molecules,” he said. “In the second study, we took advantage of vibrating molecules inside the fiber interacting with different light beams. This is a way of using one strong laser of a particular color and producing many colors, from blue to green to yellow to red to infrared.”

    The laser pulse used was 200 picoseconds long. A picosecond is one-trillionth of a second. Combining the produced light colors in such a fiber could create pulses 200,000 times shorter – a femtosecond (one quadrillionth of a second).

    (Via ACM TechNews)

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  • ESO VLT Laser Optics

    The ESO’s Very Large Telescope (I love that name, nicely to-the-point) shoots a sodium-exciting laser towards the center of the Milky Way to create an artificial “star” of light in the sky, helping calibrate its adaptive optics system. Sort of like white balancing your camera, but much, much cooler looking.

    Photo credit: ESO/Y. Beletsky

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  • Binocular Diplopia and the Book of Kells

    How did reclusive monks living in the year 700 or 800 AD draw the intricate lines of the Book of Kells, rendered by hand at sub-millimeter resolution (about the same level of detail as the engraving work found on modern money), hundreds of years before optical instruments became available, hundreds of years before the pioneering visual research of Alhazen? According to Cornell paleontologist John Cisne’s theory, their trick was in the detail and pattern: by keeping their eyes unfocused on the picture plane, the monks could superimpose their linework and judge the accuracy against the template using a form of temporary binocular diplopia (sort of like willing yourself to view a stereograph or one of those Magic Eye posters).

    That’s amazing.

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  • Transformation optics as misdirection

    From Nature, Optics: All Smoke and Metamaterials (subscription might be required, actual research publication available from the American Physical Society):

    Seeing is believing — a naive assumption in the case of an illusion device proposed by Lai and colleagues at the Hong Kong University of Science and Technology, and described1 in Physical Review Letters. The new device has the power to ‘act at a distance’ and therefore covertly alter an object’s appearance such that it has no apparent physical connection to the light scattered by the object — although this becomes increasingly difficult to achieve the farther the illusion device is from the object. Lai and colleagues1 outline a mathematical formalism proving that it is theoretically possible to grab the rays of light emitted by a given object and to reconstruct them so that they seem to come from a completely different object.

    Using metamaterials with refractive indexes less than zero to disguise the origin or content of reflected light. Not sure that I entirely understand this idea, but it’s sort of like the fabled “cloaking device”, except that instead of rendering an object invisible it actually renders it as a different object. Things will be weird fifty years from now.

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