Manifestation of periodically modulated laser beams resonance self-action in saturated absorption spectra and beam propagation

We present the results of full time-space modeling of the propagation of a frequency-modulated transversely limited beam through a near-resonant two-level saturable absorber. The model based on the direct solution of Maxwell-Bloch equations allowed us to study the transient behavior of resonant self-action of the beam at modulation periods approaching the relaxation times and to find its specific manifestations in the dependence of the output beam intensity on the instantaneous frequency. The dependence of the asymmetry and the shift of the absorption peaks upon the modulation frequency and shape is studied. Possible applications in laser spectroscopy and nonlinear optical measurement of the medium relaxation parameters are discussed.