# Laboratoire Collisions Agrégats Réactivité - UMR5589

Université Paul Sabatier - Bat. 3R4 - 118 route de Narbonne 31062 Toulouse Cedex 09, France

## Coherent Control of the Effective Susceptibility through Wave Mixing in a Duplicated Two-Level System

We theoretically demonstrate the coherent control of the effective susceptibility of a duplicated two-level system. The control is obtained for a linearly polarized weak field in the presence of a much stronger orthogonally polarized field. For small optical depths, the effective susceptibility chieff behaves as chiline2iphi (chilin is the linear susceptibility, phi the phase shift) allowing coherent control of the optical response. For large optical depths, chieff[approximate]chilin*, turning an absorber into an amplifier without affecting the dispersion.

doi:10.1103/PhysRevLett.101.213601

Voir en ligne : Phys. Rev. Lett. 101, 213601 (2008)