Theory of Pulse-Shaping by Saturable Optical Materials

Abstract

As a high‐intensity monochromatic light pulse passes through a material containing two‐level systems, saturable absorption or amplification of the radiation may occur. The resultant ``shaping'' of the intensity‐vs‐time curve as a function of distance into the sample is the subject of this paper. A theory is developed based on the Einstein rate equations, and pulse‐shape functions are derived which depend on the absorption and loss coefficients of the material, the relaxation time of the systems, the input‐pulse intensity and width, the initial ``state‐of‐pump'', and number density of absorbers in the sample.