Shaping focal field by grafted polarization

Abstract

In this paper, we propose a novel (to our knowledge) vector beam by combining the radially polarized beams with the different polarization orders, which is called the grafted polarization vector beam (GPVB). Compared with the tight focusing of traditional cylindrical vector beams, GPVB can present more flexible focal field patterns by adjusting the polarization order of two (or more) grafted parts. Moreover, because the GPVB possesses the non-axisymmetrical polarization state distribution, which will lead to the spin-orbit coupling in its tight focusing, it can obtain the spatial separation of spin angular momentum (SAM) and orbital angular momentum (OAM) in the focal plane. The SAM and the OAM are well modulated by adjusting the polarization order of two (or more) grafted parts. Furthermore, we also find the on-axis energy flow in the tight focusing of the GPVB can be changed from positive to negative by adjusting its polarization order. Our results provide more modulation freedom and potential applications in optical tweezers and particles trapping.

Versatile Optical Tweezer by Geometric Metalens with Phase‐Tailored Focusing Trajectory

“…Recently, inspired by plant grafting, the grafted vortex beams have been proposed to generate azimuth-asymmetric OAM distribution. [56][57][58] Based on our strategy, grafted optical vortex with arbitrary "scions" and "rootstocks", i.e., complex OAM distribution, can be controlled by introducing piecewise functions to the original equation ϕ n = l𝜃 n . Here, 2D rings with geometrical parameters same as the first design in Figure 2 are considered with three piecewise linear distributions of phase, corresponding to left, middle, and right panels in Figure 4, where we have deliberately set different signs for adjacent pieces for a better distinguishment.…”

Vector Beams with Only Transverse Intensity at Focus

“…2023, 13, 12519 2 of 10 two other vector beams was considered-the upper part of the beam had one order, and the lower half had another order. Initially, there was no longitudinal spin angular momentum in these beams [19,20]: the polarization at each point of the initial beam was linear; however, with tight focusing, a nonzero longitudinal component of the spin angular momentum arose, which indicated the appearance of regions in which the polarization is elliptical. This effect is a special case of spin-orbit interaction in a tight focus.…”

“…In this paper, we will show that similar properties to azimuthally polarized beams can also be obtained for sectoral azimuthally polarized beams containing V-lines of singularity. Previously, similar piecewise continuous polarization states were investigated in [18][19][20]. In [18], optical vortices with cylindrical polarization of half-integer orders were studied.…”

“…In [18], optical vortices with cylindrical polarization of half-integer orders were studied. In [19], the focusing of cylindrical vector beams of fractional orders was numerically simulated, and in [20], a vector beam that was formed from Appl. Sci.…”