Nonlinear control of light pulses in doped optical fibers

The results of a study of nonlinear processes involving light pulses in optical fibers doped with rare-earth atoms are presented. Calculations of the linear chi((1)) and nonlinear chi((3)) susceptibilities of such media are performed for a three-level A scheme of interaction. It is demonstrated that the Kerr nonlinearity and nonlinear absorption coefficients can reach extremely high levels and can be negative. Competition between the linear and nonlinear processes in a A system makes it possible to realize compensation regimes. In these regimes, the dispersion or absorption coefficients of optical fiber material vanish, and variation in the parameters of input light pulses allows for the effective control of such a system's properties in wide ranges. Conditions for the realization of regimes with slow and fast light are obtained. The characteristics of the probe pulse in the superluminal regime are studied.