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Optical trapping forces of focused circular partially coherent beams on Rayleigh particles

Yu Chaoqun, Chen Fuchang, Zeng Jun, Huang Cheng, He Zhimin, Lin Huichuan, Zhang Yongtao, Chen Ziyang, Pu Jixiong

Optica Applicata

2022

Vol. 52, nr 4

575--583

The optical trapping forces of tightly-focused radially polarized circular partially coherent beams on Rayleigh particles are theoretically investigated. Numerical calculations are performed to study the optical trapping forces on Rayleigh particles for different initial coherent length of the incident circular partially coherent beams. The results show that the magnitude of the gradient force decreases with the reduction of the initial coherent length of the focused radially polarized circular partially coherent beams, while the balanced position (i.e., the position where the optical trapping forces becomes zero) stays constant. Moreover, the focused spot gradually elongates along the optical axis with the reduction of the initial coherent length, and the axial gradient force on Rayleigh particles also decreases gradually with the reduction of the intensity gradient in axial direction. As there exists an spherical aberrant in the focusing optical system, the focal spot in the direction of the optical axis becomes trumpet-shaped, and the optical trapping forces on Rayleigh particles change as well.

Generation of optical needle and dark channel by tight focusing of radially polarized circular partially coherent beams

Lin Huichuan, Li Yan, Zhou Xiaoming, Wang Juanjuan, Chen Ziyang, Pu Jixiong

Optica Applicata

2020

Vol. 50, nr 2

229--240

We theoretically investigate the tight focusing of radially polarized circular partially coherent(RPCPC) beams through a high numerical aperture objective. The sub-wavelength super-long optical needle and dark channel can be obtained near the focus, by engineering the source coherent length of the incident RPCPC beams. The length of the optical needle and the dark channel can be adjusted, and the obtained maximal lengths of the optical needle and the dark channel are both 22λ.The full width at half maximum of the optical needle and the dark channel are 0.6λ and 0.48λ, respectively.

Tight focusing of radially polarized beams by a devil’s vortex lens

Chen Z., Hu X., Chen X., Wang X., Pu J.

Optica Applicata

2018

Vol. 48, nr 3

389--398

Tight focusing of radially polarized beams with a devil’s vortex lens is numerically investigated. Multiple focal spots can be generated in the geometric focus when a radially polarized beam is focused by a high numerical aperture objective in the presence of a devil’s vortex lens. The position of the major focal spot shifts from the geometric focus when a devil’s vortex lens with S = 1 is employed, and the position of the focal spot can be controlled by the numerical aperture of the objective. The intensity components of the major focal spot are influenced by the vortex phase of the devil’s vortex lens. A strong longitudinal component near the optical axis is produced by a devil’s vortex lens without vortex phase, and a nearly pure transversal field is produced by a devil’s vortex lens with vortex phase.