Abstract

We investigate the waveguiding induced in a weak probe propagating in a medium of two-level atoms driven by a copropagating, intense, strongly detuned pump. We show that when the transverse profde of the pump exhibits solitonlike oscillations, similar oscillations can be induced in the transverse profile of the probe [1]. The pump acts as a spatial soliton in the sense that its transverse intensity profile displays oscillating spatial behavior due to the interplay of self-focusing and diffraction. When the probe waist size is initially narrower than that of the pump, the probe adjusts its width, after a short propagation distance, to that of the pump. It is found that the weak beam, which is created during propagation by four-wave mixing, has a significant effect on the waveguiding of the probe. Athough the waveguide effect is essentially unlimited when the effect of four-wave mixing is ignored, it becomes severely limited when the medium is optically thick and the effect of four-wave mixing becomes dominant [1]. However, it is possible to reduce the effect of four-wave mixing by phase control. By controlling the relative phases of the pump and probe lasers, both absorptive and dispersive properties may be manipulated. With a proper mechanism of phase control and appropriate phase correction scheme, the weak four-wave mixing wave can be forced to remain small during most of the propagation distance through the medium, so that the waveguiding effect can be clearly discerned. This work suggests that the importance of four-wave mixing in modifying induced waveguiding should be considered in other waveguiding schemes. The potential of phase control in manipulating the properties of propagating laser light in a sophisticated way is emphasized.

© 2000 IEEE