Parametric Resonances in the Amplitude-Modulated Probe-Field Absorption Spectrum of a Two-Level Atom Driven by a Resonance Amplitude- and Phase-Modulated Pumping Field

摘要

An analytical expression is derived for the polarization induced by a weak probe field with period-ically modulated amplitude in a two-level medium saturated by a strong amplitude- and phase-modulated res-onance field. It is shown that the absorption spectrum of the probe field includes parametric resonances, the maxima corresponding to the condition 8 = 2nT - Clw and the minima to that of 5 = (2n + 1 )F - Qw, where 5 is the probe-field detuning from the resonance frequency, lw is the modulation frequency of the probe-field amplitude, and Pis the transition line width, n= 1, 2, 3,.... At the specific modulation parameters, a substantial region of negative values (i.e., the region of amplification without the population inversion) exists in the absorp-tion spectrum of the probe field.