A theory is developed that leads to the description of the internal and gross motions of an atom interacting with an arbitrary light field. The general results are then applied to the case of a Laguerre-Gaussian (LG) mode, one of a class of modes of electromagnetic radiation that possess orbital angular momentum. A number of effects are predicted, notably, an azimuthal shift in the atomic resonance, a modified radiation pressure force, and an associated torque on the atom. It is pointed out that the effects originate in the processes of the transfer of linear and orbital angular momentum from the field to the atomic gross motion. The strengths of the effects are assessed in relation to the normal axial Doppler shift and the linear light pressure force. The motion of atoms and ions subject to the LG pressure force is studied by solving the classical equation of motion. Trajectories clearly exhibiting the effects of orbital angular momentum are displayed for a free atom and for an ion in a two-dimensional trap and in a Paul trap.A theory is developed that leads to the description of the internal and gross motions of an atom interacting with an arbitrary light field. The general results are then applied to the case of a Laguerre-Gaussian (LG) mode, one of a class of modes of electromagnetic radiation that possess orbital angular momentum. A number of effects are predicted, notably, an azimuthal shift in the atomic resonance, a modified radiation pressure force, and an associated torque on the atom. It is pointed out that the effects originate in the processes of the transfer of linear and orbital angular momentum from the field to the atomic gross motion. The strengths of the effects are assessed in relation to the normal axial Doppler shift and the linear light pressure force. The motion of atoms and ions subject to the LG pressure force is studied by solving the classical equation of motion. Trajectories clearly exhibiting the effects of orbital angular momentum are displayed for a free atom and for an ion in a two-dimensional trap and in a Paul trap.

Physical Review AJul 1, 199581 citations

Angular momentum transfer in interaction of Laguerre-Gaussian beams with atoms and molecules

Pradip Kumar Mondal, Bimalendu Deb, Sonjoy Majumder

The exchange of orbital angular momentum between a Laguerre-Gaussian beam of light and the center-of-mass motion of an atom or molecule is well known. We show that the orbital angular momentum of light can also be transferred to the internal electronic or rotational motion of an atom or a molecule provided the internal and center-of-mass motions are coupled. However, this transfer does not happen directly to the internal motion, but via center-of-mass motion. If atoms or molecules are cooled down to the recoil limit, then an exchange of angular momentum between the quantized center-of-mass motion and the internal motion is possible during the interaction of cold atoms or molecules with the Laguerre-Gaussian beam. The orientation of the exchanged angular momentum is determined by the sign of the winding number of the Laguerre-Gaussian beam. We present selective results of numerical calculations for the quadrupole transition rates in the interaction of the Laguerre-Gaussian beam with an atomic Bose-Einstein condensate to illustrate the underlying mechanism of light orbital angular momentum transfer. We discuss how the alignment of diatomic molecules will facilitate exploration of the effects of light orbital angular momentum on the electronic motion of molecules.The exchange of orbital angular momentum between a Laguerre-Gaussian beam of light and the center-of-mass motion of an atom or molecule is well known. We show that the orbital angular momentum of light can also be transferred to the internal electronic or rotational motion of an atom or a molecule provided the internal and center-of-mass motions are coupled. However, this transfer does not happen directly to the internal motion, but via center-of-mass motion. If atoms or molecules are cooled down to the recoil limit, then an exchange of angular momentum between the quantized center-of-mass motion and the internal motion is possible during the interaction of cold atoms or molecules with the Laguerre-Gaussian beam. The orientation of the exchanged angular momentum is determined by the sign of the winding number of the Laguerre-Gaussian beam. We present selective results of numerical calculations for the quadrupole transition rates in the interaction of the Laguerre-Gaussian beam with an atomic Bose-Einstein condensate to illustrate the underlying mechanism of light orbital angular momentum transfer. We discuss how the alignment of diatomic molecules will facilitate exploration of the effects of light orbital angular momentum on the electronic motion of molecules.

arXiv:1403.2881Physical Review AJun 26, 201492 citations

Polarization rotation of slow light with orbital angular momentum in ultracold atomic gases

Julius Ruseckas, Gediminas Juzeliūnas, Patrik Öhberg +1 more

We consider the propagation of slow light with an orbital angular momentum (OAM) in a moving atomic medium. We have derived a general equation of motion and applied it in analyzing propagation of slow light with an OAM in a rotating medium, such as a vortex lattice. We have shown that the OAM of slow light manifests itself in a rotation of the polarization plane of linearly polarized light. To extract a pure rotational phase shift, we suggest to measure a difference in the angle of the polarization plane rotation by two consecutive light beams with opposite OAM. The differential angle $\ensuremath{\Delta}{\ensuremath{\alpha}}_{l}$ is proportional to the rotation frequency of the medium ${\ensuremath{\omega}}_{\text{rot}}$ and the winding number $l$ of light, and is inversely proportional to the group velocity of light. For slow light the angle $\ensuremath{\Delta}{\ensuremath{\alpha}}_{l}$ should be large enough to be detectable. The effect can be used as a tool for measuring the rotation frequency ${\ensuremath{\omega}}_{\text{rot}}$ of the medium.We consider the propagation of slow light with an orbital angular momentum (OAM) in a moving atomic medium. We have derived a general equation of motion and applied it in analyzing propagation of slow light with an OAM in a rotating medium, such as a vortex lattice. We have shown that the OAM of slow light manifests itself in a rotation of the polarization plane of linearly polarized light. To extract a pure rotational phase shift, we suggest to measure a difference in the angle of the polarization plane rotation by two consecutive light beams with opposite OAM. The differential angle $\ensuremath{\Delta}{\ensuremath{\alpha}}_{l}$ is proportional to the rotation frequency of the medium ${\ensuremath{\omega}}_{\text{rot}}$ and the winding number $l$ of light, and is inversely proportional to the group velocity of light. For slow light the angle $\ensuremath{\Delta}{\ensuremath{\alpha}}_{l}$ should be large enough to be detectable. The effect can be used as a tool for measuring the rotation frequency ${\ensuremath{\omega}}_{\text{rot}}$ of the medium.

arXiv:0706.0477Physical Review ANov 16, 200759 citations

Interaction of an Atomic Gas with Light Carrying Orbital Angular Momentum

G. F. Quinteiro, P. Grinberg, Christian Tomás Schmiegelow

Conference on Lasers and Electro-OpticsJan 1, 20190 citations

l

of light, and is inversely proportional to the group velocity of light. For slow light the angle $\ensuremath{\Delta}{\ensuremath{\alpha}}_{l}$ should be large enough to be detectable. The effect can be used as a tool for measuring the rotation frequency ${\ensuremath{\omega}}_{\text{rot}}$ of the medium.