Measurement of steep dispersion associated with magnetically assisted gain in Zeeman degenerate two-level system of cold atoms

Abstract

We report on the measurements of magnetically assisted dispersion and gain in a Zeeman degenerate two-level system associated with the closed D2 hyperfine transition Fg = 3 → Fe = 2 cold cesium atoms. We use a Mach-Zehnder interferometer to measure the dispersive properties of this system in the presence of a magnetic field, transversal to the quantization direction, when the atomic system is excited by a coupling and a probe beams with orthogonal polarizations. We have measured the spectrum of the refraction index for different magnitudes of the external magnetic field and different coupling beam intensities. A previously published theoretical model, using a simpler atomic transition Fg = 1 → Fe = 0, accounts reasonably for the experimentally observed gain and dispersive lineshapes.