Effective multiple optical trapping of sub-micrometer particles with petal beams

Abstract

Optical tweezers are noncontact and noninvasive force transducers. Techniques for multiple optical trapping are of much interest. In this paper, we investigate, numerically, optical trapping of multiple particles using so-called petal beams by trapping every single particle in a separate petal of the focused beam. We have used the generalized Lorenz–Mie theory to compute the optical trapping forces. Results demonstrate that the intensity is equally distributed over the lobes along the intensity ring for circularly polarized petal beams, but in the case of linear polarization, the intensity is not equally distributed over the petals, which means a particle trapped by every petal of a circularly polarized beam experiences the same force. It is shown that for a particle size range, the axial trapping stiffness for the l = 4 mode of a petal beam is about threefold greater than that of the l = 1 mode, and in the lateral direction, the trapping stiffness of the l = 2 mode is about twofold greater than that of the l = 4 mode. Finally, the optimum choice of topological charge for the stronger trap stiffness based on the particle size and trapping depth is identified.

Characteristics of a Gaussian focus embedded within spiral patterns in common-path interferometry with phase apertures

“…In optical Gaussian tweezers, a tightly focused Gaussian laser beam generates a trapping force that can capture and move small particles under a microscope 26 , 27 . In an optical tweezers employed vortex beam, micrometer particles can be rotated by the twisting force originating from OAM 3 , 28 , 29 …”

Broadband Petal‐Like Raman Laser

“…LG 0,n petal-like laser can be treated as superposition of two LG 0,n vortices with opposite topological charge. High-order LG 0,n petal-like laser beams have been widely used in manipulating microparticles, [1,2] creating 2D optical vortex arrays and 3D optical trapped structure, [3,4] free space optical communication, [5,6] condensate physics, [7] tightly focusing, [8] and self-reconstruction of laser beam. [9] Therefore, methods were developed to generate high-order LG 0,n petal-like lasers.…”

Optimized anti-reflection core-shell microspheres for enhanced optical trapping by structured light beams

“…On the one hand, the use of shaped laser beams enhances the trapping forces via minimizing the light scattering 19 – 23 . Examples include using circular Airy beam for enhanced trapping efficiency of Rayleigh particles 24 , optical trapping with Laguerre–Gaussian modes with improved axial optical forces exerted on the dielectric particles 25 , optical trapping with cylindrical vector beams 21 , creation of enhanced trapping forces with complex-valued Elegant Hermitte- and Laguerre-Gaussian laser beams compared to standard Gaussian beams 26 , and effective multiple optical trapping with petal beams 27 . On the other hand, the optical and physical properties of the intended particle play an effective role in optical trap enhancement 28 – 30 .…”

“…In this paper, we bring together both structured beams and anti-reflection coated microspheres to be used in OTs. We calculate optical trapping forces exerted on core-shell microspheres of PS-silica and anatase-amorphous titania, under illumination by several structured beams such as radially polarized beam (RPB) 45 , 46 , petal beam (PB) 27 , 47 , and hard-aperture-truncated circular Airy beam (CAB) 48 – 50 , and compare them with those of a Gaussian beam commonly used in OTs. Titania core-shell microspheres in two phases (anatase core and amorphous shell), are great candidates to be used in OTs to achieve nano-Newton forces with trap stiffness greater than .…”