* Astronomy

Blobrana · L

RE: Light

Blobrana · L

Light at the speed of a bicycle and much more
The speed of light, 300 million metres per second, was long thought an immutable constant and has defined our understanding of matter and energy but recent research in the area of optics and photonics is proving that we can manipulate light to some ingenious and hugely lucrative ends.
From the use of adaptive optics to catch perfect images of distant galaxies or detailed representations inside bio-specimens of, for example, mouse embryos, to electromagnetically induced transparency which can slow light to the speed of a bicycle - the field of optics and photonics is in the scientific vanguard.
The Institute of Physics (IOP) and the Engineering and Physical Sciences Research Council (EPSRC) are launching a new report today, Wednesday, 9 September, entitled Optics and photonics: Physics enhancing our lives, to highlight the most recent advances in the field and demonstrate the potentially lucrative ends a range of researchers have in sight.

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Blobrana · L

A newly discovered repulsive aspect to light could one day control telecommunications devices with greater speed and less power, researchers said today.
The discovery was made by splitting infrared light into two beams that each travel on a different length of silicon nanowire, called a waveguide. The two light beams became out of phase with one another, creating a push, or repulsive force, with an intensity that can be controlled; the more out of phase the two light beams, the stronger the force.

"We can control how the light beams interact. This is not possible in free space - it is only possible when light is confined in the nanoscale waveguides that are placed so close to each other on the chip" - Mo Li, a postdoctoral associate in electrical engineering at Yale University.

The discovery could lead to nanodevices controlled by light rather than electricity.

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Blobrana · L

Fluidic micro lenses

Blobrana · L

Lasers

Blobrana · L

RE: Light

Blobrana · L

Light carries momentum
Since the early 20th Century physicists have known that light carries momentum, but the way this momentum changes as light passes through different media is much less clear. Two rival theories of the time predicted precisely the opposite effect for light incident on a dielectric: one suggesting it pushes the surface in the direction light is travelling; the other suggesting it drags the surface backwards towards the source of light. After 100 years of conflicting experimental results, a team of experimentalists from China believe they have finally found a resolution.
Weilong She and his colleagues from Sun Yat-Sen University have studied the effect of light at the interface of air and a silica filament and they find that light exerts a push force on the surface.

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Blobrana · L

A brilliant young physicist João Magueijo asks the heretical question: What if the speed of light - now accepted as one of the unchanging foundations of modern physics - were not constant?
Magueijo, a 40-year old native of Portugal, puts forth the heretical idea that in the very early days of the universe light travelled faster - an idea that if proven could dethrone Einstein and forever change our understanding of the universe. He is a pioneer of the varying speed of light (VSL) theory of cosmology -an alternative to the more mainstream theory of cosmic inflation- which proposes that the speed of light in the early universe was of 60 orders of magnitude faster than its present value.

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Blobrana · L

A team of University of Toronto physicists have demonstrated a new technique to squeeze light to the fundamental quantum limit, a finding that has potential applications for high-precision measurement, next-generation atomic clocks, novel quantum computing and our most fundamental understanding of the universe.
Krister Shalm, Rob Adamson and Professor Aephraim Steinberg of U of T's Department of Physics and Centre for Quantum Information and Quantum Control published their findings in the January 1 issue of the prestigious international journal Nature.

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Blobrana · L

Materials such as milk, paper, white paint and tissue are opaque because they scatter light, not because they absorb it. But no matter how great the scattering, light is always able to get through the material in question. At least, according to the theory. Researchers Ivo Vellekoop and Allard Mosk of the University of Twente have now confirmed this with experiments. By shaping the waveform of light, they have succeeded in finding the predicted open channels in material along which the light is able to move.

In materials that have a disordered structure, incident light is scattered in every direction possible. In an opaque layer, so much scattering takes place that barely any light comes out at the back. However, even a material that causes a great deal of light scattering has channels along which light can propagate. This is only possible if the light meets strict preconditions so that the scattered light waves can reinforce one another on the way to the exit.
By manipulating the waveform of light, Vellekoop and Mosk have succeeded in finding these open channels. They used an opaque layer of the white pigment, zinc oxide, which was in use by painters such as Van Gogh. Only a small part of the original laser light that falls on the zinc oxide, as a plane wave, is allowed through. As every painter knows, the thicker the paint coating, the less light it will let through. By using information about the light transmitted to programme the laser, the researchers shaped the waveform to the optimum form to get it to pass through the open channels.
To this end, parts of the incident wave were slowed down to allow the scattered light to interfere in precisely the right manner with other parts of the same wave. In this way, Vellekoop and Mosk increased the amount of light allowed through by no less than 44 percent. As theoreticians had predicted, open channels can always be found and transmission through them is, furthermore, independent of the thickness of the material concerned.

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