February 12, 2009

Researchers from the Technion and the Weizmann Institute: Thermal Atoms Can Freeze Images

Images imprinted on light rays and propagating in free space lose their sharpness after a short distance – a phenomenon called diffraction. Researchers from the Technion and the Weizmann Institute discover a method of eliminating this phenomenon in a special thermal atomic medium

Researchers from the Technion and the Weizmann Institute have found a way to eliminate the phenomenon of diffraction, which causes images carried by light rays to lose their sharpness. Their work was recently published in the scientific journal “Physical Review Letters.”

“We are at the height of an information revolution and an enormous effort is being invested in improving technology for processing, transmitting and storing information,” the researchers explain. “One of the most fascinating research areas is all-optical data processing, in which researchers explore systems that process optical data without having to convert it to electronic or digital data. These systems are expected to dramatically speed up data processing. In particular, there is a lot of interest in transmission and processing of images. One of the difficulties in implementing all-optical systems for image processing is the distortion that occurs to the images during their movement through open space due to diffraction. The more data the image stores and the higher its resolution, the faster the distortion is. In imaging systems, such as a camera or the eye, lenses are used in order to recover the original image, but such recovery depends on the quality and size of the lens and cannot be used in many cases.”

In the recently-published work, the Technion researchers – doctoral student Ofer Firstenberg, Dr. Moshe Shuker and Prof. Amiram Ron, plus Prof. Nir Davidson of the Weizmann Institute – present a special atomic medium, in which the optical diffraction is completely eliminated. The medium, called “electromagnetically induced transparency medium,” contains a dilute vapor of atoms at room temperature. In this medium, it is possible to cause the image to travel at a speed that is 100,000 times slower than the speed of light and to utilize the thermal movement of the atoms in order to “drag” or “push” the light moving through them. The researchers discovered that by fine tuning of the interaction between atoms and light, it is possible to cause the atoms to push the diffracted light rays back to their original path. Every image which enters this medium will move through it and emerge on the other side without distortion.

Many future applications can utilize this method. Optical correlation between two images can enable rapid, automatic identification of patterns, such as objects or people, in images. For this purpose, it is necessary to slow down the image movement and prevent distortion caused by diffraction. In addition, by this means, it is possible to trap light rays in a small area inside the atomic vapor. For optical microscopes, diffraction is one of the main limitations and preventing it will enable the improvement of the microscopes under certain conditions.

Pictured: An explanation of the process

Technion spokesman, Amos Levav: 052-4524873