RADIATION TRANSFORMATION USING STIMULATED RESONANT SCATTERING OF LIGHT WITH A SMALL FREQUENCY-SHIFT

A theory of stimulated scattering and generation of light with a small frequency shift (\omega - omega0\T1 less-than-or-equal-to 1) in a res onant absorbing medium is developed. In the approximation of tracing p olarization, a set of equations governing stimulated resonant ring (SR S) is derived for arbitrary powers of pulses of the pump and scattered radiation. The resonant polarization of a medium in the field of two waves is represented as a series of Fourier harmonics with multiple sp atial frequencies. The amplitudes of the Fourier harmonics are given b y integrals of modified Bessel functions of the corresponding orders. Spectral threshold characteristics of nonstationary SRS are studied. T he threshold pump power for SRS at the periphery of an absorption line is much less than the saturation power. This fact allows the implemen tation of phase conjugation for a spatially inhomogeneous pump with a small frequency shift. Depending on the sign of the frequency detuning of the pump with respect to the center of the absorption line, Stokes or anti-Stokes SRS occurs. The frequency shift of SRS increases with a growth of the pump power. The stationary oscillation regime of a las er using SRS in the scheme of a quasilongitudinal pump is investigated . Within the Born approximation, an expression for the reflection coef ficient is derived for an SRS laser. Such a laser is considered to be a system with frequency-nondegenerate self-phase conjugation of the pu mp through light-induced four-wave interaction. It is demonstrated tha t, at pump intensities lower than the saturation intensity the reflect ion coefficient R in such a system may exceed 10(-2).