ADDITIONAL 10% OFF - Coupon Code:GN10

Two laser pointer beams of the same intensity

Now add time reversal operation, which is similar to rewinding a video tape and watching its action from back to front. For example, the time reversal action of the balloon inflation process is to deflate the same balloon. In optics, the time-reversal counterpart of the amplification gain medium is the absorption loss medium. If a system can return to its original configuration after symmetric and time reversal operations, it is considered that the system meets the parity-time symmetry condition.

Soon after the discovery of the anti-laser pointer, scientists have predicted that a system with parity-time symmetry will be able to support both lasers and anti-lasers at the same frequency in the same space. In the device created by Zhang and his research team, the size of the gain and loss, the size of the constituent unit, and the wavelength of the light passed together constitute the condition of parity-time symmetry. When the system is in equilibrium and the gain and loss are equal, there is no net amplification or net absorption of light. However, if the conditions are disturbed and the symmetry is broken, then coherent amplification and absorption can be observed.

Laser Pointer 532nm Visible Beam Light

In the experiment, two beams of the same intensity are directed to opposite ends of the device. The researchers found that by changing the phase of a light source, they can control whether the light waves spend more time in the amplifying material or in the absorbing material. Speeding up the phase of a light source will result in an interference pattern that is conducive to gain medium or coherent light amplification, or called lasing mode. Slowing down the phase of a light source has the opposite effect, leading to more time spent in the lossy medium and coherent absorption of the beam, or so-called flyback mode.

If the phases of these two wavelengths are equal, and they enter the device at the same time, they will neither be amplified nor absorbed, because the light takes equal time in each area. The researchers set the target wavelength at about 1556 nanometers, which is within the band used for optical communications. This green laser pointer work is the first demonstration of a balanced gain-loss example that strictly satisfies the parity-time symmetry condition, leading to the realization of simultaneous lasing and flyback.

The co-author of the paper said that he used to be a postdoctoral researcher in the laboratory and is now an assistant professor of electrical engineering at the University of Buffalo. The successful realization of lasing and flyback in a single integrated device is a big step towards the ultimate light control limit. He is also a professor and director of the National Science Foundation Nanoscience and Engineering Center at the University of California, Berkeley. This work was mainly funded by the US Department of Energy's Office of Science, and used the Molecular Factory, a user facility of the Department of Energy's Office of Science located in the Berkeley Laboratory.

Researchers found the path of the laser pointer through opaque materials