Amplification of short light pulses with a spherical wavefront

The propagation of a conical light beam through an optical amplifier is considered. The theoretical analysis is based on an analogue of the system of Frantz–Nodvik equations taking into account the specific character of spherical waves. The conditions of applicability of reduced equations (in slowly-varying amplitude approximation) for describing spherical waves propagating in a nonlinear medium are formulated. The peculiarities of amplification for different values of the beam divergence are compared. The change in the transverse structure of a diverging beam, which appears due to the amplification saturation, is studied.