Conical emission as a result of self-phase modulation in samarium vapor under the near-resonant condition

We studied the conical emission in samarium (Sm) vapor under the near-reson ant condition. The incident dye laser was tuned to the transition line, 4f( 6)6s(2) F-7 --> 4f(6)(F-7)6s6p(P-1(0)) (lambda = 562.601 nm), of the Sm ato m. Using a high-temperature oven, we could obtain the atomic density of 8 x 10(14) atoms/cm(3), large enough to observe the conical emission. We obser ved one to three rings around the original laser beam, and the number of th e rings depended on the laser intensity, the laser wavelength, and the atom ic density. These results are attributed to the self-phase modulation of th e laser beam interacting with the near-resonant atomic medium. We give a si mple expression that describes the dependence of the locations of the rings on the laser intensity. We compare the experimental results with this expr ession quantitatively and then estimate the nonlinear susceptibility of Sm vapor. (C) 2001 Optical Society of America.