Number 120, March 26, 1993 by Phillip F. Schewe and Ben Stein LIGHT WAVES CAN BE USED AS A LENS to focus a beam of neutral atoms, creating the possibility of a fundamentally new form of submicron lithography. At the APS meeting in Seattle this week, Gregory Timp of AT&T Bell Labs reported on an experiment in which a stream of sodium atoms, cooled to mK temperatures in an "optical molasses" setup and gently steered by the electric fields of an optical standing wave, were deposited on a silicon substrate in a series of closely spaced (less than 300 nm) lines. A comparable grating pattern can be created using transmission electron microscopy, but Timp believes that his line spacings and line widths can be greatly reduced as his technique is further refined. Furthermore, he hopes that with additional focusing he will be able to produce not just well collimated lines but also spots (quantum dots). Sodium atoms are easy to manipulate but are chemically reactive and therefore not suitable for doing lithography, so Timp will try indium atoms next. At the same meeting, Robert Celotta of NIST reported on the laser manipulation of neutral chromium atoms. CARBON BUCKYTUBES are nanoscopic in width but potentially macroscopic in length. Richard Smalley of Rice University said at the APS meeting that he had tapered to a thin point one of the two graphite electrodes used in making fullerenes (in an electric arc) and that he hoped to use this configuration to make nanotubes with lengths of centimeters or more. Such tubes would be stronger than any other known fiber, according to Smalley, and because of its nm diameter would be invisible to the eye (besides which you would cut your hand trying to hold one). Actually the nanotubes produced so far (only microns in length) usually appear not singly but in bundles and groups of bundles in a tendon-like hierarchy. The tubes can also be concentric and can be used as containers for lead atoms (which, squeezed into a line only a few atoms abreast, constitute the world's thinnest wire); these discoveries were reported in January by scientists at NEC Corporation in Japan. Thomas Ebbeson of NEC said at the APS meeting that his colleagues were now also studying other metals in addition to lead, and that carbon nanotubes may be useful for studying one-dimensional chemistry. POLYMERS CAN BE USED TO MAKE HOLOGRAMS . At the APS meeting, W.E. Moerner of IBM Almaden reported on the optical properties of a new polymer, a composite chain molecule called PVK:F-DEANST:TNF. In this material the photorefractive effect---a nonlinear optical effect in which laser light causes the migration and then selective storage of charges in various parts of the polymer---is particularly strong, as strong as in some conventional inorganic photorefractive crystals. Moerner has already used the polymer to make a 125-micron-thick hologram in which two laser beams are combined to write and read information. If the diffraction efficiency, one measure of the brightness of the hologram image, could be improved from the current 1% to as high as 10%, then potential applications could ensue. These include erasable, high-density, rapid-access storage of information (eventually the Encyclopedia Britannica stored on a dime-sized hologram). Polymer holograms will be cheaper and more easily formable than inorganic crystalline holograms, said Moerner.