Simultaneous slow and fast light involving the Faraday effect
B. Macke, Bernard Ségard
We theoretically study the linear transmission of linearly polarized light pulses in an ensemble of cold atoms submitted to a static magnetic field parallel to the direction of propagation. The carrier frequency of the incident pulses coincides with a resonance frequency of the atoms. The transmitted light, the electric field of which is transversal, is examined in the polarizations parallel and perpendicular to that of the incident pulses. We give explicit analytic expressions for the transfer functions of the system for both polarizations and for the corresponding group delays. We demonstrate that slow light can be observed in a polarization, whereas fast light is simultaneously observed in the perpendicular polarization. Moreover, we point out that, due to the polarization postselection, the system is not necessarily minimum phase shift. Slow light can then be obtained in situations where an irrelevant application of the Kramers-Kronig relations could lead one to expect fast light. When the incident light is step modulated, we finally show that, in suitable conditions, the system enables one to separate optical precursor and main field.
arXiv:1606.00736•Physical Review A•Oct 3, 2016•7 citations