Interaction of atom with non-paraxial Laguerre-Gaussian beam:Forming superposition of vortex states in Bose-Einstein condensates

TL;DR

This paper develops a microscopic theory for the interaction between non-paraxial Laguerre-Gaussian beams and Bose-Einstein condensates, enabling the creation of superpositions of vortex states beyond the paraxial approximation.

Contribution

It introduces a novel scheme to generate superpositions of vortex states in BECs using focused optical vortices with non-paraxial beams, considering coupled angular momenta transfer.

Findings

Superposition of vortex states can be created with focused LG beams.

Two-photon Rabi frequencies depend on focusing angles and OAM/SAM configurations.

Vortex-antivortex structures and interference of three vortex states are demonstrated.

Abstract

The exchange of orbital angular momentum (OAM) between paraxial optical vortex and a Bose-Einstein condensate (BEC) of atomic gases is well known. In this paper, we develop a theory for the microscopic interaction between matter and an optical vortex beyond paraxial approximation. We show how superposition of vortex states of BEC can be created with a focused optical vortex. Since, the polarization or spin angular momentum (SAM) of the optical field is coupled with OAM of the field, in this case, these angular momenta can be transferred to the internal electronic and external center-of-mass (c.m.) motion of atoms provided both the motions are coupled. We propose a scheme for producing the superposition of matter-wave vortices using Gaussian and a focused Laguerre-Gaussian (LG) beam. We study how two-photon Rabi frequencies of stimulated Raman transitions vary with focusing angles for different combinations of OAM and SAM of optical states. We demonstrate the formation of vortex-antivortex structure and discuss interference of three vortex states in a BEC.