Conical emission from atomic vapors excited by nearly resonant laser beams

Eve A. Chauchard, Y.H. Meyer

Mark Bashkansky, Philip R. Battle, Rita Mahon +1 more

Petros Zerom, Robert W. Boyd

Dmitriy I. Chekhov, Dmitri V. Gaidarenko, Alexei G. Leonov +2 more

Won-Kyu Lee, Young-Chul Noh, Jin-Ho Jeon +4 more

We studied the conical emission in samarium (Sm) vapor under the near-resonant condition. The incident dye laser was tuned to the transition line, 4f66s2 7F→4f6(7F)6s6p(1P0)(λ=562.601 nm), of the Sm atom. Using a high-temperature oven, we could obtain the atomic density of 8×1014 atoms/cm3, large enough to observe the conical emission. We observed one to three rings around the original laser beam, and the number of the rings depended on the laser intensity, the laser wavelength, and the atomic density. These results are attributed to the self-phase modulation of the laser beam interacting with the near-resonant atomic medium. We give a simple expression that describes the dependence of the locations of the rings on the laser intensity. We compare the experimental results with this expression quantitatively and then estimate the nonlinear susceptibility of Sm vapor.

Donald J. Harter, Robert W. Boyd

Experimental evidence is presented that shows that the conical emission often found surrounding a near-resonant laser beam after it passes through an atomic vapor is due to nondegenerate four-wave mixing enhanced by the ac Stark effect. We demonstrate self-trapping of a pulsed dye-laser beam in sodium vapor for wavelengths 0.04 to 10 A shorter than that of the D(2) resonance and show that the four-wave mixing process leading to conical emission occurs within these self-trapped filaments.