Phase sensitive non-linear absorption in an N system - Andal Narayanan

Coherent control of absorption and dispersion of electromagnetic fields by atomic systems, is made possible using the effect of Coherent Population Trapping (CPT). It was shown recently [1] that, the effects of CPT in three level atomic systems connected by three electromagnetic fields, enables the control of coherence effects induced by any two appropriately chosen fields, through the intensity and relative phase of the third field. In general, for a closed system made of atomic levels and EM fields, the populations and coherences become sensitive to the relative phase between the applied fields. In this talk, the results of an experimental investigation of phase dependent control, seen in such closed three level systems, extended to an N system, will be presented [2]. It is shown that the reactive Kerr non-linearity seen traditionally in N systems becomes phase dependent [2]. In view of this, we argue that, for properly chosen N systems, this gives rise to the possibility of developing an optical switch, controlled by the phase of a microwave field. [1] Electromagnetically induced transparency controlled by a microwave field Hebin Li at. al, Phys. Rev. A Vol. 80, 023820 (2009) [2] Phase sensitive microwave optical double resonance in an N system, T.M. Preethi et. al, Euro Physics Letters, Vol. 95, 34005 (2011)