A material whose optical properties can be modified on a small scale by laser light promises a wide range of applications
Properties of small areas of a versatile optical film can be tweaked by applying ultrashort pulses of laser light, A*STAR researchers show1. This tunability makes the material suitable for various light-based applications, from lenses to holograms.
When the shutter button on a camera is depressed, it focuses by electrically adjusting the positions of the constituent parts of the lens. Similarly, the parameters of optical components in many devices and scientific instruments are adjusted by moving their parts, or by stretching or heating them. Being able to use light to adjust optical components would offer many advantages, including fast response and easy integration into small and robust systems.
Now, such an optically adjustable system has been developed by Qian Wang of the A*STAR Institute of Materials Research and Engineering and co-workers, along with collaborators at the University of Southampton, UK, and the Nanyang Technological University, Singapore.
The team studied a material widely used in CD and DVD disks — chalcogenide glass. In rewritable CD and DVD data-storage devices, microsecond or nanosecond (10−9 second) laser pulses are used to switch the medium between two states — crystalline and disordered. In contrast, Wang and her team used a tightly controlled series of much shorter femtosecond (10−15second) optical pulses to set the glass into incremental states between completely crystalline and completely disordered. By scanning the focused laser beam across the glass film, they could modify regions as small as about 0.6 micrometers (see image).