PHOTON ABSORPTIONS OF A DRIVEN 3-LEVEL ATOM IN A SQUEEZED VACUUM

A three-level ladder atom driven by two coherent laser fields with rat her different frequencies in various kinds of reservoirs is considered . Making use of the master equation and Bloch equation, we calculate n umerically and show graphically the steady-state populations versus tw o-photon detuning. We also discuss and compare the two-photon and one- photon processes occurring for various cases. For a squeezed vacuum, o nly when the carrier frequency of the squeezed vacuum equals the avera ge of frequencies of the two driving fields and the phase matching con dition is fulfilled, will there be a strong two-photon resonant absorp tion from the squeezed vacuum, a characteristic different from absorpt ion of photons from a classical field; Otherwise, the two-photon ab-so rption rate from the squeezed vacuum will be greatly diminished.