Number 257 (Story #2), February 6, 1996 by Phillip F. Schewe and Ben Stein|
OPTICAL BULLET HOLES , non-light-absorbing circles on an otherwise absorbing material, have been shown theoretically to be stable and to exist on microscopic scales, offering the possibility for a new type of optical memory scheme. Based on a model developed by researchers at the University of Strathclyde in Scotland (contact Willie Firth, firstname.lastname@example.org), the scheme would involve using a saturable light-absorbing material inside a cavity. Turning on a uniform, constant background light field and then shining very short pulses of light on the material can create two-dimensional bullet holes; essentially, what is happening is that the absorber is being excited at specific locations into a high-energy state, preventing it from taking in any further light. "Unlike real bullet holes, optical bullet holes can be moved around," say the researchers. This is done by locally changing the phase of the background light field, creating a matrix of attracting spots that can pull the bullet holes into new locations. "Of course a message or picture could be written by a volley of bullets, just as in cowboy cartoons," says Firth. But these optical bullet holes, which can be made as tiny as 10 optical wavelengths according to the model and possibly smaller, can potentially be used to store and manipulate computer bits. One advantage of this scheme is that the regularly spaced attracting spots could control the position of the bullet holes, serving as a kind of error correction mechanism. Collaborating teams across Europe are planning to implement these ideas and demonstrate them experimentally in such materials as organic solids and semiconductor microstructures. (W.J. Firth and A.J. Scroggie, upcoming article in Phys. Rev. Letters).