BRAIDED LIGHT. An intense beam of laser light, traveling through a nonlinear optical medium, will alter the index of refraction in its vicinity. Physicists at UCLA have calculated that when two such beams travel in close, parallel lines through a plasma, they can braid around each other (see figure at Physics News Graphics). In other words, an effective light-light attraction occurs because of nonlinear reactions in the plasma.

UCLA scientist Chuang Ren (310-794-4457, ren@physics.ucla.edu) says that such a braiding effect might be useful in optical steering applications and, in nature, might occur when intense photon fluxes filament as they emanate from supernovas and powerful celestial gamma ray sources. Experimental studies are about to proceed at UCLA and at the Instituto Superior Tecnico in Portugal. (Ren et al., Physical Review Letters, 4 September /pnu/2000/; Select Articles.)