arXiv subjects

O. V. Angelsky

Publications and source records attributed to O. V. Angelsky.

3 recordsLinked to original sources

arXiv2026

Controllable localization and manipulation of optical hollow traps by means of optical-vortex diffraction

An optical vortex (OV) is coupled with the local intensity zero and is thus a field configuration suitable for "hollow" optical traps and optical tweezers. When an incident circular OV beam experiences diffraction at a rectilinear screen edge (SE), and the conditions of weak diffraction perturbation (the SE is far enough from the beam axis) are fulfilled, the main consequence is the OV-core displacement from its initial (axial) position. Based on the model of incident Laguerre-Gaussian (LG) beam, we investigate analytically and numerically the ways of controlling the OV-core position in the diffracted-field cross section by means of changing the SE position with respect to the incident-beam axis. The results show that regulating the SE position with ~1 mcm accuracy (which is available for existing mechanical tools), controllable OV-core motion with a sub-nanometer accuracy can be realized. Possible modifications of this motion depending on the incident beam topological charge, wavefront curvature, SE properties (semitransparent screen, phase-step screen) and the distance between the diffraction plane and the observation plane are analyzed. The conditions most favorable for the micro-object trapping and manipulation are specified and discussed.

physics.optics↗

arXiv2012

Scattering of inhomogeneous circularly polarized optical field and mechanical manifestation of the internal energy flows

Based on the Mie theory and on the incident beam model via superposition of two plane waves, we analyze numerically the momentum flux of the field scattered by a spherical microparticle placed within the spatially inhomogeneous circularly polarized paraxial light beam. The asymmetry between the forward- and backward-scattered momentum fluxes in the Rayleigh scattering regime appears due to the spin part of the internal energy flow in the incident beam. The transverse ponderomotive forces exerted on dielectric and conducting particles of different sizes are calculated and special features of the mechanical actions produced by the spin and orbital parts of the internal energy flow are recognized. In particular, the transverse orbital flow exerts the transverse force that grows as a^3 for conducting and as a^6 for dielectric subwavelength particle with radius a, in compliance with the dipole mechanism of the field-particle interaction; the force associated with the spin flow behaves as a^8 in both cases, which testifies for the non-dipole mechanism. The results can be used for experimental identification and separate investigation of the spin and orbital parts of the internal energy flow in light fields.

physics.optics↗

arXiv2011

Orbital rotation without orbital angular momentum: mechanical action of the spin part of the internal energy flow

It is known that internal energy flow in a light beam can be divided into the orbital flow, associated with the macroscopic energy redistribution within the beam, and the spin flow originating from instantaneous rotation of the field vectors inherent in circular or elliptic polarization. In contrast to the orbital one, experimental observation of the spin flow constituent seemed problematic because (i) it does not manifest itself in the visible transformation of the beam profile and (ii) it converts into the orbital flow upon tight focusing of the beam, usually employed for the energy flow detection by the mechanical action on probe particles. We propose a two-beam interference technique that permits to obtain appreciable level of the spin flow in moderately focused beams and to detect the orbital motion of probe particles within a field where the transverse energy circulation is associated exclusively with the spin flow. This result can be treated as the first demonstration of mechanical action of the spin flow of a light field.

physics.optics↗