Light-induced magnetization of a gas of optically polarized atoms

Fahime Ghashghaei, Alireza Rashedi, Farrokh Sarreshtedari +1 more

Abstract Distribution of the atomic polarization in a Cesium vapor cell, induced by optical pumping, is analytically calculated and discussed when an external magnetic field interacts with the system. Based on the rate equations of the optically pumped atomic system and considering the effect of magnetically induced dichroism on the absorption of polarized propagating light, we have obtained the light intensity and atomic polarization distribution along the propagation direction of the gas cell. It is shown that based on the initial light polarization and the laser detuning, the external magnetic field considerably changes the polarization distribution. The obtained results of the polarization distribution versus applied magnetic field can be used for different investigations, including the study of the atomic magnetometer’s sensitivity.

A. I. Alekseev

A. I. Alekseev

A. I. Alekseev

The optically induced magnetic moment of a stationary atom is calculated as a function of time and the resonance detuning ω-ω ba to within a constant factor having the dimensions of a magnetic moment based on the symmetry of an atom in the field of a resonant light pulse and symmetry with respect to time reversal including the initial conditions. The even dependence of the optically induced magnetic moment on ω-ω ba for an elliptically polarized pulse with an isotropic initial state of the atom and its odd dependence on ω-ω ba in the case of a linearly polarized pulsed with an anisotropic initial state in the atom’s alignment are shown to be consequences of symmetry with respect to time reversal and the initial conditions. This behavior is retained even after passage of the light pulse, when the resulting relaxation destroys the time reversal symmetry. The optically induced magnetization of an atomic gas is found to have analogous properties.

A. I. Alekseev, M. E. Alferieff

A. I. Alekseev

The properties of the density matrix and the multipole moments arising in oriented and aligned atoms with zero nuclear spin through the interaction with strong resonant ultrashort pulses with wave vector k 0 and circular or linear polarization have been found. Calculations have been made for the time-dependent light-induced magnetization μ ( t ′) of a gas of pre-oriented and prealigned atoms following the passage of a weak resonant elliptically polarized pulse with frequency ω and wave vector k collinear with k 0 . It is shown that for oriented atoms, μ ( t ′) is an even function of the detuning from resonance, ω-ω ba , and can be split into two terms whose directions are a consequence of symmetry and are determined by the vectors k 0 and k as well as by the direction of rotation of the electric fields corresponding to the pulses. For aligned atoms the vector μ ( t ′) is collinear with k , and the first term is an even function of ω-ω ba . However, the second term is an odd function of ω-ω ba and reverses direction when the sign of ω-ω ba changes, as well as when the orientation of the axes of the polarization ellipse is changed. It is shown that if a series of weak linearly polarized pulses pass through the gas, the light-induced magnetization of the oriented and aligned gas atoms can be decomposed into three factors: the first determines the direction and is a consequence of the symmetry; the second (with the dimensions of magnetic moment) depends on the characteristics of the resonant transitions; and the third is a universal function of t ′ and ω-ω ba that does not depend on the underlying characteristics of the resonant transition. These vector factors and the universal functions are in principle different for oriented and aligned atoms.