Slow photons as charged Quasi-Particles

Recently we have proposed the method of Raman Adiabatic Transfer of Optical States (RATOS) to manipulate the optical state of light. A four-level atomic medium in double-Lambda configuration is interacting with two pump fields and a signal photon with very slow group velocity. An adiabatic change in time of the pump fields can then generate a slow photon in a superposition of different frequencies. Here we theoretically analyze the influence of an adiabatic change in the spatial form of the pump fields. We demonstrate that the signal photon then behaves like a charged quasi-particle: in paraxial approximation its dynamics is governed by a Schroedingerlike equation that includes a scalar and a vector potential whose form is determined by the shape of the pump fields. We suggest pump field configurations that generate potentials corresponding to a constant electric and a constant magnetic field. In both cases the center of a Gaussian signal pulse follows the trajectory of corresponding classical point particles. In the case of a quasi-magnetic field the dispersion of the pulse is reduced. We give an intuitive interpretation of this effect, which may have application as a waveguide of light inside an atomic vapor. Furthermore, we devise a scheme of pump fields that generates a vector