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Focus shaping of the radially polarized Bessel–Gauss beam with a sine-azimuthal variation wavefront

Gao X, Zhang D., Mei T., Fu R., Zhuang S.

Optica Applicata

2013

Vol. 43, nr 3

567--582

Focusing properties of the radially polarized Bessel–Gauss beam with a sine-azimuthal variation wavefront was investigated by the vector diffraction theory. The wavefront distribution is the sine function of the azimuthal angle with one phase parameter that indicates the phase change frequency. Results show that the focal pattern can be altered by the phase parameter, and many novel focal patterns may occur, such as multiple dark-foci focal pattern, crescent shape, and wheel shape. For case of a higher phase beam, the whole focal pattern turns on a symmetric wheel shape with multiple reduplicate intensity elements. When the phase parameter is an odd number, the number of reduplicate elements equals the phase parameter, while when the phase parameter is an even number, the number of reduplicate elements is two times the phase parameter. In addition, the effect of the phase parameter on the focal pattern is more considerable than that of the beam parameter under low numerical aperture. Under higher numerical aperture, the effect of the beam parameter on the focal pattern gets stronger.

Focus shaping of Bessel-Gauss beam with radial varying polarization

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

Optica Applicata

2012

Vol. 42, nr 3

481-491

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.