Exploiting the circular polarization of light to obtain a spiral energy flow at the subwavelength focus

Orbital Energy and Spin Flows in a Strong Focus of Laser Light

“…In this work, which continues the research reported in Ref. [6], we derive analytical relations for all projections of the orbital and spin flows in the focal plane of a strongly focused left-hand circularly polarized Gaussian beam, also calculating a torque exerted upon a dielectric ellipsoidal microparticle in the focus of the beam and discussing results of an experiment on rotating the microparticle around its center of mass.…”

“…A number of works [1][2][3][4][5][6] have reported on the appearance of the orbital angular momentum in the strong focus of a conventional circularly polarized Gaussian beam, which was then transferred to a microparticle placed in the focal spot. This phenomenon is related to the spin-to-orbital light momentum conversion.…”

“…Meanwhile, a transverse energy flow is observed in the strong focus, leading to the non-zero longitudinal projection of the orbital angular momentum. Spin-orbit interaction in sharp focus has already been studied in works [1][2][3][4][5][6], but there is no detailed description of SAM and OAM within the Richards-Wolf formalism [7]. The Richards-Wolf theory (RWT) [7], which describes the electromagnetic field near the sharp focus, was generalized for the case of a plane interface near the focus [8].…”

“…The larger is the focal length compared to the wavelength, the more accurate is this method. This method has been successfully applied for theoretical analysis in [1][2][3][4][5][6]. In other works [8][9][10][11][12], RWF allowed obtaining other physical quantities in the sharp focus, like energy flow density and spin flow density, orbital angular momentum, and spin angular momentum.…”

Minimal Focal Spot Size Measured Based on Intensity and Power Flow

“…The projections of the electric field near the focus for the initial field in Equation (7) have the form [ 31 ]: …”