1 School of Physics Science and Engineering, Zhengzhou University, Zhengzhou 450001, China;
2 National Key Laboratory for Laser Fusion, Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China;
3 Information and Telecommunication Company of State Grid Henan Electric Power Corporation, Zhengzhou 450001, China;
4 Key Laboratory of Nano-Fabrication and Novel Devices Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
We propose an efficient method of generating a vortex beam with multi-foci by using a fractal spiral zone plate (FSZP), which is designed by combining fractal structure with a spiral zone plate (SZP) in the squared radial coordinate. The theoretical analysis reveals that the number of foci that embed vortices is significantly increased as compared with that obtained by using a conventional SZP. Furthermore, the influence of topological charge on the intensity distribution in focal plane is also discussed in detail. For experimental investigation, an FSZP with topological charge p=1 and 6.4 mm diameter is fabricated by using a photo-etching technique. The calibration indicates that the focusing performances of such a kind of zone plane (ZP) accord well with simulations, thereby providing its potential applications in multi-dimensional optical manipulation and optical imaging technology.
Project supported by the National Natural Science Foundation of China (Grant Nos. 11404290 and 61505178), the Major National Scientific Instruments Developing Special Project (Grant No. 2012YQ130125), the Postdoctoral Science Foundation of Henan Province, China (Grant No. 2013008), the Program for Science & Technology Innovation Talents in Universities of Henan Province, China (Grant No. 172102210481), and the Key Scientific Research Projects in Universities of Henan Province, China (Grant No. 19B140005).
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