Quadrupole Interaction of Non-diffracting Beams with Two-Level Atoms

Recently it has been shown that the quadrupole interactions can be improved significantly as the atom interacts at near resonance with the Laguerre-Gaussian (LG) mode. In this paper, we illustrate that other kinds of optical vortex can be also led to a considerable enhancement of quadrupole interaction when the atom interacts with optical modes at near resonance. The calculations are performed on an interesting situation with Cs atom, where the process is concerned with dipole-forbidden and quadrupole-allowed transitions with a convenable choice of atomic and optical mode parameters. In this direction, we show that the quadrupole transitions can be significantly enhanced and therefore they can play an interesting role and lead to new features of atom-light interaction, which can have some constructive implications in experiments.Comment: 9 pages, 10 figure

Quadrupole absorption rate for atoms in circularly-polarized optical vortices

Twisted light beams, or optical vortices, have been used to drive the circular motion of microscopic particles in optical tweezers and have been shown to generate vortices in quantum gases. Recent studies have established that electric quadrupole interactions can mediate an orbital angular momentum exchange between twisted light and the electronic degrees of freedom of atoms. Here we consider a quadrupole atomic transition mediated by a circularly-polarized optical vortex. We evaluate the transfer rate of the optical angular momentum to a $Ca^+$ ion involving the $4^2S_{1/2}\rightarrow 3^2D_{5/2}$ quadrupole transition and explain how the polarization state and the topological charge of the vortex beam determine the selection rules.Comment: 13 pages, 4 figures. arXiv admin note: substantial text overlap with arXiv:2007.0402