Laser s friend
ever since the first ruby laser was demonstrated in the early 1960s, many different kinds of lasers have been fabricated. These include dye lasers, semiconductor lasers and gas lasers. Laser light is extremely intense and of a single colour. Because of their unique properties, lasers can be employed in a number of areas. They have been used, among other things, to accurately measure the distance to the moon (by bouncing laser pulses off a reflector on the moon), to vaporise materials (from diamonds to retinas), for optical communications in fiber optics and in compact disc players.
Now, researchers from the University of Arizona and the California Institute of Technology have developed a new synthetic resin that will allow scientists to use laser light for a number of novel applications ranging from device fabrication to chemical synthesis ( Nature , Vol 398, No 6722).
The researchers have synthesised a highly sensitive resin that absorbs not one but two photons at a time. When a very intense beam of laser is bombarded on the resin, the patch in which the laser is focused gets polymerised. By focusing the laser on different parts of the resin, a pattern of chemical changes can be imposed on the resin.
This process can be used in a host of applications. Chemical reactions can now be activated in tiny regions rather than in whole samples. Any information can be coded by a string of fluorescent binary bits. In the developing field of nanotechnology, one can build extremely small structures. The team has demonstrated the fabrication of a photonic crystal by using this resin. These are honeycomb structures that exclude or trap light at select wavelengths. The pattern was polymerised using laser light and the unwanted resin was washed away chemically. The resulting pattern acted as a photonic crystal.