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 Å shorter than that of the D2 resonance and show that the four-wave mixing process leading to conical emission occurs within these self-trapped filaments.
© 1982 Optical Society of America
Donald J. Harter and Robert W. Boyd, "Conical emission due to four-wave mixing enhanced by the ac Stark effect in self-trapped filaments of light," Opt. Lett. 7, 491-493 (1982)