Evolution of light beams in polarization and direction

Guoan Cai, Zhaoying Wang

ABSTRACT The manipulation mechanisms of the hybrid Poincaré beam (HPB) on the spatial coherence and circular dichroism of a polarized atomic ensemble are investigated. The inherent spatial polarization distribution of the HPB can establish position‐dependent and selective interaction channels with different Zeeman sublevels of atoms. By applying an external static magnetic field, the dynamic modulation of atomic spatial coherence and circular dichroism based on different magnetic field orientations can be analyzed. To characterize this process, this article innovatively employs the Stokes parameters distribution and polarization ellipse parameters of the transmitted light spot as direct observational methods. The evolution trajectory of the polarization state is directly mapped onto the Poincaré sphere, enabling a visual representation of the optical field's polarization state. This method intuitively reveals the continuous evolution of atomic polarization characteristics under different orientation magnetic fields, thereby transforming the microscopic quantum control process into macroscopic and clear polarization transmission images.

Philippe Réfrégier

Christian Delsart, J. Keller, V.Paul Kaftandjian

The dynamic Stark effect (Autler-Townes splitting and radiative shift) of a J = 0 ↔ J = 1 optical transition have been investigated. The barium atomic beam is illuminated by a strong pump beam, resonant or slightly non-resonant with the BaI resonance line (λ = 5 535 Å) ; the fluorescence induced by a weak probe beam is detected versus the probe frequency. With linear polarizations for the two beams one deals either with a two-level (parallel polarizations) or with a three-level system (perpendicular polarizations). In the latter case and for small detunings of the pump beam, the Autler-Townes doublet has been observed. For large detunings of the pump beam a single, shifted resonance has been obtained with both polarization settings. In the three-level case the observation of the passage from the Autler-Townes situation to the light-shift situation, is reported. The corresponding calculations are presented; a particular attention is paid to the case of large detunings for the pump beam (light-shift situation). The evolution calculated for the resonance curve (position and relative intensities of the peaks) when the relative polarization directions are changed is consistent with the experimental data.

A. M. Khachatryan, N. V. Shakhnazaryan

Stefan Nimmrichter

Muhammad Suhail Zubairy

Maxwell showed that light consists of electric and magnetic fields that oscillate in directions perpendicular to the direction of propagation. Associated with this picture of light as an electromagnetic wave is an important property—the polarization of light. The polarization of light is related to the direction of oscillation of the electric field in an electromagnetic wave. In this chapter, the basic principles of quantum mechanics are discussed by studying the polarization property of a single photon. First the properties of a polarizer are presented and Malus’ law for polarized light is derived. Next it is shown that the basic features of quantum mechanics can be understood via an analysis of a single photon passing through a polarizer. This simple system allows an introduction of Dirac’s ket and bra notations for a quantum state. Finally the transformation properties of the quantum beam splitter and the polarization beam splitters are discussed.