Optics

French artist Paul Gauguin has had quite the resurgence - having a painting sell for nearly $300 million will do that - but the artist noted for his colorful paintings of Tahitian life was also a highly experimental printmaker.

The techniques and materials Gauguin used to create his unusual and complex graphic works are little studied but a team from Northwestern University and the Art Institute of Chicago used a simple light bulb, an SLR camera and computational power to uncover new details of Gauguin's printmaking process -- how he formed, layered and re-used imagery to make 19 unique graphic works in the Art Institute's collection.
A team has undertaken what they call the most comprehensive examination of skyglow -  variations in the radiance of the night sky - ever done and found remarkably large variations in artificial night sky brightness at the different observation sites.  

Light became popular because it allowed us to extend the day - and electricity meant people could read a book without falling asleep and setting themselves on fire. But the introduction of light into the nighttime environment is one of the most striking changes humans have made to the Earth’s physical environment, and it is associated with several unintended negative consequences. One example is skyglow, the artificial brightening of the night sky.

A collaboration of researchers have experimentally produced Möbius strips from the polarization of light, confirming a theoretical prediction that it is possible for light's electromagnetic field to assume this peculiar shape. 

Möbius strips are easy to create, of course. Millions of school children do it in classrooms every year by taking a strip of paper, twisting it once and joining up the ends. That's it, you have created a Möbius strip: a three dimensional structure that has only one side.

But finding Möbius strips occurring naturally is another issue.

Engineers in Austria have given us a blessing and a curse - they have created a giant laser system that sends beams in different directions, which makes them visible from many different angles. 

The angular resolution is so fine that the left eye is presented a different picture than the right one, creating a 3D effect.


Image: FastLizard4 / flickr 

By:  Charles Q. Choi, Inside Science

(Inside Science) - A laser could be created with air in a practical way, a new advance that could one day be used to help spot explosives or pollutants from afar, researchers say.

Laser light is generated by pumping energy into atoms or other objects. A chain reaction can occur in which energized atoms all stimulate each other to give off laser light.
A terrestrial laser scanning technique that allows the structure of vegetation to be 3D-mapped to the millimeter is more accurate in determining the biomass of trees and carbon stocks in forests than current methods, according to a paper in Methods in Ecology and Evolution

The study authors believe it could be used in monitoring carbon stocks for climate policy. Both above-ground biomass and carbon stocks are important details for UN-REDD, the United Nations initiative on Reducing Emissions from Deforestation and forest Degradation that is striving to keep the destruction of forests in check and thereby preserve the uptake of carbon by trees.

A new optical technique by which audio information can be extracted from high-speed video recordings, by using an image-matching process based on vibration from sound waves.

The technique is based on the fact that sound waves are mechanical waves that cause air to vibrate when traveling, the paper notes. That vibration through air can cause vibration of objects located in its traveling path, especially if the objects are lightweight, thin, and flexible, such as a piece of paper. The vibrations, although usually with small amplitudes, can be detected and analyzed algorithmically, and audio reconstructed based on those calculations.


On a quest to design an alternative to the complex approaches currently used to produce electrons within microwave electron guns, a team of researchers have demonstrated a plug-and-play solution capable of operating in a high-electric-field environment with a high-quality electron beam.

Unfamiliar with microwave electron guns? They provide a higher current and much higher quality electron beams than conventional DC guns for X-ray sources . Beams of this sort are also used in free-electron lasers, synchrotrons, linear colliders and wakefield accelerator schemes. But the electron emission mechanisms involved -- laser irradiation of materials (photocathodes) and heating of materials (thermionic cathodes) -- tend to be complex, bulky or extremely expensive.


Laser-powered weapons have been a staple of science-fiction movies for so long we think we know what they would look like, but we really don't.

Researchers at the Laser Centre of the Institute of Physical Chemistry of the Polish Academy of Sciences and the Faculty of Physics, University of Warsaw decided to find out, and make a real film of it. They fired an ultrashort laser pulse through the air and captured it on video and when they slowed it down they found that it looks lot like a regular bullet, and a lot like a "Star Wars" light saber - combined. 


A long-distance optical tractor beam can move tiny particles - one fifth of a millimeter in diameter - a distance of up to 20 centimeters, which is almost 100 times further than previous experiments.


The hollow laser beam is bright around the edges and dark in its center and it can be used to attract or repel objects.

Get ready to control the weather or capture an X-Wing fighter in space - if it's really close, that is.



Dr. Vladlen Shvedov (L) and Dr. Cyril Hnatovsky adjust the hollow laser beam in their lab at the Australian National University. Credit: Stuart Hay, ANU