Steady-state population inversion of multiple Ξ -type atoms by the squeezed vacuum in a waveguide

Abstract

We study the dynamics of multiple $\mathrm{\ensuremath{\Xi}}$-type atoms driven by a squeezed vacuum reservoir in a quasi-one-dimensional waveguide. We show that the atomic system's steady state is a pure state, and a complete population inversion can occur when the dipole moment of the second transition is almost perpendicular to the polarization of the incident squeezed light. We also prove that the steady state of the system is the direct product of that in the single-atom case with modified squeezed vacuum even when dipole-dipole interaction is involved. This steady-state population inversion may be used to study the two-photon laser or collective atomic effect.