STUDY OF THE ABSORPTIVE AND DISPERSIVE RESPONSE ON THE RESONANT NONDEGENERATE 4-WAVE-MIXING SIGNAL

We study in this article the topological properties in the frequency space, of the absorption and the refraction index for the resonant non-degenerate four-wave mixing signal. This space is defined by the pump- and probe-filed frequencies, omega1 and omega2, respectively. Our model treats the strong pumping beam to infinite order whereas the weaker signal and probe beams are approximated to first order. We solve the density matrix equations in frequency domain and the propagation equations for the different fields. We consider explicitly the space variation for the pumping field as it covers its optical path. Our results show that the oscillations of population at the detuning pumping-probe frequency, which are responsible for the appearance of the coherent gain dips, are strongly influenced by the effects of field propagation, chemical concentration of the active material, and the magnitude of the inhomogeneous broadening of the spectral absorption line.