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1

Focusing of linearly polarized helico-conical Lorentz beam with sine-azimuthal variation wavefront

Bao Y., Lan J., Miao Y., Zhang D., Gao X.

Optica Applicata

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2018

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Vol. 48, nr 3

373--387

EN

In this article a theoretical research is described into focusing of a linearly polarized helico-conical Lorentz beam with a sine-azimuthal variation wavefront. The simulation results show the vortex charge on the axis, which has an obvious modulation effect on the focal modes of the Lorenz beam under certain beam parameters and phase parameters. Both the phase parameter and the vortex charge are zero, the focal spot appears round. The focal spot is symmetric about y axis when the charge is 0 and the phase parameter is adjusted. And the focal evolution patterns vary remarkably under different beam parameters and the phase parameters. In the process of focus evolution, there appears some novel focal patterns, such as a circle, a “T”, a butterfly, a small running humanoid, a whale tail, a flower of four leaves, a serpentine, a goldfish, a Chinese knot and an octopus, which indicates that the focus mode of the optical vortex Lorentz beam can be altered by changing the phase parameters and vortex charge.

2

Focusing properties of partially coherent dark hollow Gaussian beams through a thin lens system

Dong Y., Zhao C., Wang K., Zhao C., Cai Y.

Optica Applicata

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2015

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Vol. 45, nr 2

151--161

EN

This paper investigated the focal shift of partially coherent dark hollow Gaussian beams through a thin lens system. An analytic expression of the irradiance distribution of the focusing partially coherent dark hollow Gaussian beams in the back focal plane has been given by using the Collins formula. The focus shift of focused partially coherent dark hollow Gaussian beams in different parameters is studied in detail by numerical calculations. It is found that the absolute value of the focal shift of partially coherent dark hollow Gaussian beams decreases as the transverse coherence width or the order of the dark hollow Gaussian beams or a parameter of the dark hollow Gaussian beams increases.

3

Focus shaping of Bessel-Gauss beam with radial varying polarization

Gao X., Fu R., Shen H., Dong X., Geng T., Zhuang S.

Optica Applicata

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2012

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Vol. 42, nr 3

481-491

EN

Focusing properties of Bessel-Gauss beam with radial varying polarization are investigated based on vector diffraction theory in this article. The polarization angle formed by polarization direction and radial coordinate is the function of the radial distance in pupil plane, and one polarization parameter indicates the speed of change of polarization angle. It was found that the intensity distribution in focal region can be altered considerably by the beam parameter and polarization parameter. For a small beam parameter, the focal spot broadens transversely, distorts into ring focus, and then evolves back into focal spot on increasing polarization parameter. When beam parameter gets higher, focal pattern becomes complicated and the focus evolution principle with increasing beam parameter also changes significantly. Some novel focal patterns may appear, including multiple intensity rings, dark hollow focus, cylindrical crust focus.

4

Conditions for tighter focusing and higher focal depth of radially polarized vector beam

Gao X, Wang Q, Yun M, Yu J, Guo H, Zhuang S

Optica Applicata

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2012

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Vol. 42, nr 1

85--101

EN

The radially polarized vector beam has attracted much attention recently and was also used to obtain a smaller focal spot. In this paper, highly focusing properties of radially polarized vector beam are investigated by comparing them with those of linearly polarized beam. A condition was found for tighter focusing of radially polarized vector beam. The focal spot of radially polarized vector beam is not always smaller than that of linearly polarized beam. Even if only a longitudinal field component is considered, in fact, the condition for tighter focusing of radially polarized vector beam is very complicated. Therefore, more attention should be paid to the smaller focal spot generation by means of radially polarized vector beam in practical use. In addition, the focal depth of radially polarized beam decreases on increasing numerical aperture under condition of small radius ratio, and increases on increasing radius ratio. The focal depth difference between these two kinds of beams shrinks upon increasing radius ratio and numerical aperture.

5

High focusing of radially polarized Bessel-modulated Gaussian beam

Gao X., Gao M., Hu S., Guo H., Wang J., Zhuang S.

Optica Applicata

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2010

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Vol. 40, nr 4

965--974

EN

The focusing properties of radially polarized Bessel-modulated Gaussian (QBG) beam are theoretically investigated in detail by vector diffraction theory. The QBG beam contains an optical vortex. Calculation results show that the intensity distribution in focal region of radially polarized QBG beam can be altered considerably by changing beam parameter and the topological charge of the optical vortex. Beam parameter can induce remarkable focus evolution in axial direction. While topological charge adjusts intensity distribution more significantly in transverse direction, for instance, one focal spot changes into one ring pattern. And some novel focal patterns may occur, including two-peak focus, one ring focus, two-ring focus, three-ring focus, and even dark hollow focus, which is very important in optical tweezers technique.