Magneto-optical control of the group velocity of light in an inhomogeneously broadened medium

We investigate the use of a magnetic field, in conjunction with an elliptically polarized laser field, to control the group velocity of light in an inhomogeneously broadened medium. We show both theoretically and experimentally that the dispersion and hence, the speed of light in an atomic system, having V-configuration with Zeeman sublevels as their excited states, can be effectively controlled magneto-optically. We present approximate analytical solutions for a homogeneously broadened medium and numerical solutions for both a homogeneously and an inhomogeneously broadened medium. We show that while one can tune the speed of light from subluminal to superluminal with the magnetic field in a static or cooled medium with V-type atoms, in hot atoms one can achieve an efficient magneto-optical tunability in the subluminal regime. We experimentally demonstrate such control of light speed using a single elliptically polarized light and a moderately strong magnetic field in a 87Rb vapor cell. We propose to use the optical field for coarse control and the magnetic field for finer control of the light speed in an atomic medium.