线偏振相位涡旋光束的像散特性

Astigmatic characteristics of linearly polarized phase vortex beam

提出采用像散系数表征涡旋光束的像散特性。利用螺旋相位板产生了线偏振相位涡旋光束,并对其光束质量及像散特性进行了实际测量。数值模拟了不同拓扑荷数的涡旋光束的传输特性及光束质量,分析了像散系数随拓扑荷数变化的规律,结果表明:当拓扑荷数为整数时,光束无像散,像散系数为零;当拓扑荷数为半奇数时,光束的像散特性明显,像散系数达到极大值;随着拓扑荷数整数部分的增加,像散系数的极大值减小。

The linearly polarized phase vortex beam has a unique spiral phase distribution and central singularity.The topological charge of the vortex beam can be integral and fractional.The integral vortex beam has a ring light intensity distribution with dark spots in the center,while the fractional vortex beam has a unique radial gap,which belongs to the non-rotational symmetric beam and has astigmatic characteristics.In this paper,the astigmatism coefficient is proposed to characterize the astigmatism characteristics of vortex beam.A linearly polarized phase vortex beam is generated by using a spiral phase plate.Its beam quality and astigmatism characteristics are measured.The propagation characteristics and beam quality of vortex beam with different topological charge is numerically simulated,and the astigmatism coefficient changing with topological charge is analyzed.The results indicate that when the topological charge is integer,the beam has no astigmatism and the astigmatism coefficient is zero;when the topological charge is semi-odd,the astigmatism characteristic of the beam is obvious,and the astigmatism coefficient reaches the maximum;as the integral part of topological charge increased,the maximum value of astigmatism coefficient decreases.