Knots of Light

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This article, graphics, and derivatives are posted by permission. Google Translate was used on the original article in German, edited to native English by Admin.

Super-light illustration 900x831.jpg

Image © Bonn University by permission

Bonn Physicists make super-Photon

—A novel light source with multiple applications
Date: 22/11/2010

Physicists at Bonn University have established a completely new light source, called a Bose-Einstein condensate of photons. Until recently, experts had considered this an impossibility. This method is also suitable for the design of innovative laser-like light sources that radiate in the X-ray range. This breakthrough may possibly afford fabrication techniques for more powerful computer chips. The scientists reported their discovery in the November issue of the journal Nature (doi: 10.1038/nature09567).

By cooling, rubidium atoms and concentrating them into a small space, they suddenly become indistinguishable: They behave like a single huge "superparticle". Physicists call this a Bose-Einstein condensate.

For "light particles", the photons would have to actually form the condensate. Unfortunately, this idea fails in one fundamental problem: If one photon is "cooled", it disappears. To cool light and to focus light at the same time seemed impossible, therefore, until a few months ago. However, the Bonn physicists Jan Klare, Julia Schmitt, Dr. Frank, and Professor Dr. Martin Weitz have now succeeded —a minor sensation.

How warm is the light?

If one heats the tungsten filament of an incandescent bulb, it begins to glow - first red, then yellow and finally blue. A "temperature" may be assigned in this way to each color of light: e.g., blue light is hotter than red. Tungsten glows with a different color than iron, for instance. Physicists calibrate the color temperature by an imaginary object model, the so-called black body. If one were to heat up this body to 5,500 degrees, the same color is produced as sunlight at noon. In other words, midday light 5,500 degrees Celsius, or nearly 5,800 Kelvin. (The Kelvin temperature scale has no negative values, but starts at absolute zero temperature of -273 degrees centigrade, so the Kelvin values are always 273 degrees higher than the corresponding C-values).

If a black body is cooled, the light radiated will, at some point, no longer be in the visible range, but rather, emits only invisible infrared photons. At the same time the black body's radiation intensity is decreasing: The amount of photons with decreasing temperature is always lower. This trend makes it very difficult to form a Bose-Einstein condensation from a necessary amount of cooler photons.

The technique used by the team at Bonn University uses two highly reflective, parallel mirrors, reflecting and trapping a light beam reflecting between the mirrors. Between the reflective surfaces, were dissolved dye molecules with which the photons collide regularly. In these collisions, the photons were absorbed into the molecules, then emitted again. "It brought the photons to the temperature of the dye-liquid," explains Professor Weitz. "So it cools to room temperature, promptly."

A condensate of light

Superphoton 11 906x603.jpg

The Bonn physicists next increased the number of photons between the mirrors, by stimulating the dye solution with a laser. This allowed them to focus the light particles and sufficiently cool them to the level that the light became a condensed "super-Photon".

This photonic Bose-Einstein condensate is a completely new light source with laser-like properties. This also offers a distinct advantage over lasers, "We can now establish a laser to produce very short wavelength light - in other words such as UV or X-ray light," said Jan Klare, "Using a photonic Bose-Einstein condensate."

This prospect should please especially chip designers: They use laser light to engrave logic circuits in their semiconductor materials. How fine these structures will be limited, among other things, by the light wavelength: Long wavelength lasers are less suitable for fine work that are short wavelength —like trying to sign a letter with a paintbrush.

X-ray radiation is a much shorter wavelength than visible light. X-ray lasers should therefore accommodate, in principle, on the same silicon area significantly more complex circuits. This will enable a new generation of high-performance chips - and more powerful computers for the end user. In other applications such as spectroscopy or photovoltaics, the method could also be useful.

Prof. Dr. Martin Weitz Prof. Dr. Martin Weitz
Institut für Angewandte Physik der Universität Bonn Institute of Applied Physics, University of Bonn
Telefon: 0228/73-4837 oder -4836 Phone: 0228/73-4837 or -4836
E-Mail: E-mail: Martin.Weitz @

Jan Klärs January Klare
Telefon: 0228/73-3453 Phone: 0228/73-3453
Institut für Angewandte Physik der Universität Bonn Institute of Applied Physics, University of Bonn
E-Mail: E-mail: 

Illustration © DEM

New kind of light created in physics breakthrough

Physicists describe new particles as super photons
By Clara Moskowitz
updated 11/24/2010 2:20:12 PM ET LiveScience

Physicists have created a new kind of light by chilling photons into a blob state.


Just like solids, liquids and gases, this recently discovered condition represents a state of matter. Called a Bose-Einstein condensate, it was created in 1995 with super-cold atoms of a gas, but scientists had thought it could not be done with photons, which are basic units of light. However, physicists Jan Klärs, Julian Schmitt, Frank Vewinger and Martin Weitz of the University of Bonn in Germany reported accomplishing it. They have dubbed the new particles "super photons."


“To trap the photons, the researchers devised a container made of mirrors placed very, very close together — about a millionth of a meter (1 micron) apart. Between the mirrors, the researchers placed dye molecules — basically, little bits of color pigment. When the photons hit these molecules, they were absorbed and then re-emitted.”


The mirrors trapped the photons by keeping them bouncing back and forth in a confined state. In the process, the light packets exchanged thermal energy every time they hit a dye molecule, and they eventually cooled down to about room temperature.


While room temperature is nowhere near absolute zero, it was cold enough for photons to coalesce into a Bose-Einstein condensate.

See also

Original article in German

Transliteration at Google translate

Scientists Create Light Knots (holographically, by computer using the mathematics of light)

Twisted Physics
By Jeanna Bryner, LiveScience Managing Editor
17 January 2010 01:01 pm ET
Their results, detailed online Jan. 17 in the journal Nature Physics, are "firsts" for a couple of reasons. While so-called knot theorists have studied mathematical equations similar to dark knots, the new research created these knots with math functions that followed rules of propagating light. In addition, unlike other dark knots created that have been tangled up with other knots, Dennis and his colleagues produced isolated dark knots within the light beam, he said.
"For me, it shows how physicists can adapt existing pure mathematics, such as knot theory, and find it manifest in physical phenomena," Dennis said. "It also shows how finely we can control the flow and propagation of laser light using holograms. This degree of control is likely to find applications in future laser devices.