In the present paper two-photon near resonant interaction of a three-level system with intense ultrashort light pulse is investigated (Fig. 1). This problem has been studied by several authors,1-3 but a complete interpretation is not yet available. The quasienergy method simplifies the calculations and gives an obvious physical interpretation to the results. When analyzing the dynamics of the atomic level populations a nonmonotonic dependence of the populations vs pump intensity was revealed. For definite values of the system parameters, the increase in the field strength decreases the atomic susceptibility. In the case of two-pump pulses a region of anomalous dispersion is discovered for the susceptibility of the medium (Fig, 2). Such nontrivial behavior of populations is characteristic only of multilevel systems and opens wide the possibilities for light pulse operation.
© 1989 Optical Society of AmericaPDF Article