Two-pulse conical yoked superfluorescence in Rb vapor

Summary form only given.We have observed yoked superfluorescence (YSF) on the 5D-6P-5S channel in atomic rubidium after two-photon excitation of the 5D-5S transition by a short (3 ps), 778-nm pulse from a Ti:sapphire laser system. The excitation pulse is formed by a pair of spatially overlapping pulses of wave vectors k/sub 1/ and k/sub 2/ where |k/sub 1/|=|k/sub 2/|=2/spl pi///spl lambda/ and /spl lambda/ is the wavelength of the 5D-5S transition. When the atoms are excited by taking one photon from along k/sub 1/ and one from along k/sub 2/, then phase matching requires that the yoked transition consists of photon pairs along k/sub DP/ and k/sub PS/ where k/sub 1/+k/sub 2/=k/sub DP/+k/sub PS/ and k/sub DP/ and k/sub PS/ are the wave vectors of, respectively, the upper (5D-6P) and the lower (6P-5S) transition components of the YSF. The YSF pulses are emitted in a cone determined by Brownell et al. (1995). This conical emission of YSF was observed on the 420 nm lower transition. The measured behavior of the conical apex angle /spl beta/ as a function of the angle between the excitation pulses /spl alpha/ is given as a series of points and shows good agreement with the solid line based on Brownell et al.