The Voigt Effect for a Polarized Dense Alkali Vapor in a Small Magnetic Field*

The magneto-optical Voigt effect occurs when light is propagating through a material placed in a magnetic field which is perpendicular to the direction of propagation. The goal of this research is to study whether the Voigt effect can be used to determine the spin polarization of a dense, optically pumped alkali vapor with a relatively small magnetic field. To our knowledge, the formalism for the Voigt effect in these conditions has not been previously calculated. For this calculation, the polarizability tensor of the alkali was obtained using time-dependent perturbation theory. This tensor was used to estimate the effect on the probe beam’s polarization and amplitude as it passes through the gas. This work demonstrated that the Voigt rotation angle has a quadratic dependence on the spin polarization of the alkali. The next step in our research is to use this result to measure the polarization of such alkali vapors, which are used to produce hyperpolarized 3He targets for research in nuclear physics.