[1] [1] LITVIN I A, FORBES A. Intra-cavity flat-top beam generation［C］//Optics Express, 2009, 17(18):15891-15903.

[2] [2] MA H T, LIU Z J, ZHOU P, et al. Generation of flat-top beam with phase-only liquid crystal spatial light modulators［J］. Journal of Optics, 2010, 12(4): 045704.

[6] [6] DE SAINT DENIS R, PASSILLY N, LAROCHE M, et al. Beam-shaping longitudinal range of a binary diffractive optical element［J］. Applied Optics, 2006, 45(31): 8136-8141.

[7] [7] BELAFHAL A, NEBDI H. Generation and propagation of novel donut beams by a spiral phase plate: Humbert beams［J］. Optical and Quantum Electronics, 2014, 46(1): 201-208.

[8] [8] BURGER L, LITVIN I, NGCOBO S, et al. Implementation of a spatial light modulator for intracavity beam shaping［J］. Journal of Optics, 2015, 17(1): 015604.

[9] [9] KIM D J, KIM J W. Direct generation of an optical vortex beam in a single-frequency Nd: YVO4 laser［J］. Optics Letters, 2015, 40(3): 399-402.

[10] [10] LIU J S, TAGHIZADEH M R. Iterative algorithm for the design of diffractive phase elements for laser beam shaping［J］. Optics Letters, 2002, 27(16): 1463-1465.

[11] [11] YANG G Z, DONG B Z, GU B Y, et al. Gerchberg-Saxton and Yang-Gu algorithms for phase retrieval in a nonunitary transform system: a comparison［J］. Applied Optics, 1994, 33(2): 209-218.

[13] [13] MOH K J, YUAN X C, BU J, et al. Generating radial or azimuthal polarization by axial sampling of circularly polarized vortex beams［J］. Applied Optics, 2007, 46(30): 7544-7551.