Frequency comb polarization spectroscopy of multilevel rubidium atoms

We present a theoretical and experimental study of the polarization effects obtained in 87Rb room temperature atoms excited by an optical frequency comb. The rotation of the linearly-polarized weak optical field (probe) occurs when a strong circularly-polarized coupling (pump) beam breaks the degeneracy of the system and thereby introduces birefringence into the medium. Resonant excitation of the rubidium atoms by circularly-polarized optical frequency comb results in redistribution of angular momentum states that gives a net spin polarization to the medium due to the optical pumping. The density matrix formalism is used to calculate the atom-light interaction and obtained Zeeman sublevel populations were taken for modeling polarization spectra on the D1 transition in the rubidium atom. Modeled polarization signals based on induced optical anisotropy are in very good agreement with obtained experimental results