Light Bends by Itself
OK, now my brain hurts.
Any physics student knows that light travels in a straight line. But now researchers have shown that light can also travel in a curve, without any external influence. The effect is actually an optical illusion, although the researchers say it could have practical uses such as moving objects with light from afar.
It's well known that light bends. When light rays pass from air into water, for instance, they take a sharp turn; that's why a stick dipped in a pond appears to tilt toward the surface. Out in space, light rays passing near very massive objects such as stars are seen to travel in curves. In each instance, light-bending has an external cause: For water, it is a change in an optical property called the refractive index, and for stars, it is the warping nature of gravity.
For light to bend by itself, however, is unheard of—almost. In the late 1970s, physicists Michael Berry at the University of Bristol in the United Kingdom, and Nandor Balazs of the State University of New York, Stony Brook, discovered that a so-called Airy waveform, a wave describing how quantum particles move, can sometimes bend by a small amount. That work was largely ignored until 2007, when Demetri Christodoulides and other physicists at the University of Central Florida in Orlando generated optical versions of Airy waves by manipulating laser light, and found that the resultant beam curved slightly as it crossed a detector.
How did this self-bending work? Light is a jumble of waves, and their peaks and troughs can interfere with one another. For example, a peak passing a trough cancels each other out to create darkness; a peak passing another peak "interferes constructively" to create a bright spot. Now, imagine light emitted from a wide strip—perhaps a fluorescent tube or, better, a laser whose output has been expanded. By carefully controlling the initial position of the wave peaks—the phase of the waves—at every step along the strip, it is possible to make the light traveling outward interfere constructively at only points on a curve and cancel out everywhere else. The Airy function, which contains rapid but diminishing oscillations, proved an easy way to define those initial phases—except that the resultant light would bend only up to about 8°.
More: http://news.sciencemag.org/sciencenow/2012/04/light-bends-by-itself.html
Paper1 (Sub): http://www.opticsinfobase.org/ol/upcoming_pdf.cfm?id=161557
Paper2 (Sub): http://prl.aps.org/abstract/PRL/v108/i16/e163901
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