Number 39, July 1, 1991 by Phillip F. Schewe and Ben Stein THE FIRST ALL-OPTICAL SWITCH has been created by Alan Huang at AT&T Bell Labs. Previous optical switches involved a conversion between electricity and light at some point in the process. In Huang's device, which exploits the fact that the speed of light in certain (nonlinear) media depends on the light intensity, a laser beam enters a 100-meter loop of optical fiber, splits off into two directions, and reconverges, producing an interference pattern. By sending out an additional burst of light in parallel with one of the counter-propagating beams, the interference pattern can be altered and the exit of light from the switch can be controlled. The new switch, described by Huang at the recent Physics Computing '91 conference in San Jose, CA, can currently turn on and off in only 0.5 ps, whereas all-electronic switches take at least 10 ps. With the invention of the switch, Huang believes that scientists have all the fundamental components needed to create an all-optical computer. (Science News, 22 June 1991.) THE CRYSTAL STRUCTURE OF K3C60 , face-centered cubic, has been determined by a UCLA-Stony Brook-Buffalo collaboration using x-ray diffraction techniques. This development should facilitate a better understanding of fullerite superconductivity which seems to be fully three-dimensional, unlike other organic superconductors which are quasi-one-dimensional in nature, or the copper oxides which are quasi-two-dimensional superconductors. (Nature, 20 June 1991.) CLUSTERS OF ARGON ATOMS can coexist in solid and liquid phases over a range of temperatures for a given pressure, unlike ordinary bulk matter, in which phase coexistence is only observed at a single temperature (the critical point) for a certain pressure. Based on theoretical work by Stephen Berry at the University of Chicago, UCLA experimentalist Robert Whetten and others have actually made spectroscopic measurements of argon which show both liquid and solid characteristics. Neither molecular nor bulk in nature, clusters are sometimes considered to be a fifth state of matter, in addition to solid, liquid, gas, and plasma. (Mosaic, Spring 1991.) HIGH-INTENSITY SOLAR FLARES erupted in record numbers in early June 1991. Magnetic disturbances in a small solar area are believed to be responsible for the flares, which resulted in the ejection of charged particles from the site and the production of massive amounts of electromagnetic radiation. The x rays were so intense that they saturated the detectors on board the GOES-7 satellite. Characteristic gamma rays from oxygen and carbon atoms from the sun were recorded by detectors on the Gamma Ray Observatory; these may provide details of the composition of the sun's lower atmosphere. (Science News, 22 June 1991.) RESEARCH AT AT&T BELL LABS has been reorganizing during the past year to meet more directly the business needs of the company. This shift has strengthened certain research units within the lab but has caused some scientists to look for jobs elsewhere. The June issue of Physics Today cites, for example, a reallocation of research funds away from the physical sciences and hardware toward computer systems and software development.