Abstract
The spin angular momentum and the extrinsic orbital angular momentum of light are associated with the polarization of light and the light propagation trajectory, respectively. Those momenta are interdependent not only in an inhomogeneous or anisotropic medium but even in free space. This interaction is called the spin-orbit interaction of light. The effects of the spin-orbit interaction of light manifest themselves in a small transverse shift of the beam field longitudinal component from the beam propagation axis in the waist region under the circular polarization sign change. They can be observed both for Gaussian beams and for structured beams. The effects of the spin-orbit interaction of light should be taken into account when nanophotonics devices are created, but the detailed investigation of the effect had not been performed yet due to the low intensity noise image of the beam waist. Precise measurements of the focal waist centerline are needed to determine the transverse shift of the beam field longitudinal component of the asymmetric converging beam's waist under the circular polarization sign change. We propose methods for determining the transverse and longitudinal positions of the beam waist. Computer image processing methods made it possible to obtain the value of the beam waist's transverse position with an accuracy of 0.1 mkm. These methods will allow further testing of the shifts' theoretical predictions, the values of which are the order of 1 mkm. The results obtained can also be used for laser processing of materials by polarized light and precise positioning of the beam's focal spot at a surface.
Highlights
There are three types of angular momentum of a photon: spin, intrinsic orbital, and extrinsic orbital [1]
The spin angular momentum is associated with the polarization of light [2], the light beam trajectory determines the extrinsic orbital angular momentum (OAM) [3], and the intrinsic orbital angular momentum is determined by the light field's structure of the beam [4, 5]
In the most general case, the effect manifests itself in the transverse shift from the axis of propagation of the beam reflected from the two media boundary when the circular polarization sign changes
Summary
There are three types of angular momentum of a photon: spin, intrinsic orbital, and extrinsic orbital [1]. The spin and extrinsic orbital angular momenta are interdependent in an inhomogeneous or anisotropic medium This interaction is commonly called the spin-orbit interaction of light, known as the optical Spin Hall Effect (an optical analog of the Spin Hall Effect that occurs for charge carriers in solid-state systems) [6, 7]. In the most general case, the effect manifests itself in the transverse shift from the axis of propagation of the beam reflected from the two media boundary when the circular polarization sign changes. This shift is known as the Imbert-Fedorov shift [8, 9, 10]. The transverse shifts at the core-cladding boundary result in the speckle pattern rotation of light propagating through the optical fiber under the circular polarization sign change, known as the Optical Magnus effect [11]
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