Abstract
The near-field characteristics of a radially-variant vector beam (RVVB) are analyzed by using the vectorial angular spectrum method. The non-paraxial RVVB can be decomposed into the propagating wave and the evanescent wave in near field. The coherent superposition of the longitudinal and transverse components of the RVVB results in a three-dimensional (3D) profile of the spin angular momentum flux density (SAM-FD). The evanescent wave part dominates the near field of a highly non-paraxial RVVB. The longitudinal component has a large impact on the 3D shape of the optical SAM-FD. Therefore, the 3D SAM-FD configuration of the RVVB can be manipulated by choosing the initial states of polarization arrangement. In particular, the transverse SAM-FD with a spin axis orthogonal to the propagation direction offers a promising range of applications spanning from nanophotonics and plasmonics to biophotonics.
Highlights
The characteristics of the evanescent wave for a vector optical field with radial polarization and azimuthal polarization have been reported [20,21,22]. These works indicate that the longitudinal component of both the evanescent wave and the propagating wave can be manipulated by the initial states of polarization (SoP) alignments
The three-dimensional (3D) vector structure of a highly non-paraxial vector beam may result in a 3D vector structure of the optical spin angular momentum flux density (SAM-FD) which is associated with the circular polarization [23,24]
The intensity patterns of different components of both the evanescent wave and the propagating wave are shown in Figures 2 and 3
Summary
The vector optical field with spatially-variant states of polarization (SoP) has been extensively studied because of the fundamental interest and novel characteristics it offers [1,2,3,4,5,6], such as focusing engineering [7,8], micro-particle manipulation [9,10], vectorial nonlinear optical collapse [11,12], and the optical spin-orbital angular momentum conversion in a highly non-paraxial vector beam [13]. For a highly non-paraxial vector beam, the evanescent wave [14,15] dominates the near field and the longitudinal component plays an important role in the evolution of the vector optical field. The characteristics of the evanescent wave for a vector optical field with radial polarization and azimuthal polarization have been reported [20,21,22] These works indicate that the longitudinal component of both the evanescent wave and the propagating wave can be manipulated by the initial SoP alignments. The coherent component is different from that of the transverse component Both the longitudinal and transverse superposition of the longitudinal and transverse polarization components leads to the 3D SAM‐FD component profiles of the RVVB are closely related to the initial SoP arrangement. The longitudinal dominates the near field a highly non‐paraxial superposition of the longitudinal and component transverse polarization components leads in to the. That the 3D SAM-FD of a highly non-paraxial RVVB can be manipulated by the initial SoP in the beam cross-section
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