Abstract

We study the spatial optical solitons induced in a weak nondegenerate probe beam by an intense pump beam copropagating in a Doppler-broadened atomic medium. Spatial solitons in the case of single beams have been extensively investigated [lj. The mechanism which is responsible for self-trapping is the intensity-dependent, refractive index which leads to self- focusing of the beam. Single beam solitons are formed when the effect of nonlinear refractive index compensates diffraction effects. We show that under certain circumstances a weak probe may become spatially confined due to the interplay of diffraction and pump-induced focusing of the probe. This spatial confinement is non-dissipative, that is, the probe is hardly absorbed during propagation. This is achieved by exploiting the properties of the so-called dead-zone in which, due to Doppler-broadening. the medium consisting of two-level atoms exhibits a frequency range of almost zero absorption. The almost exact cancellation of the many photons absorbed by those emitted results in low probe absorption, without affecting its relatively large refractive index. We examine realistic conditions and include pump reshaping on propagation in our calculations.

© 1998 IEEE