| SHI Changkun,SONG Yiding,DONG Bing,ZHOU Zhanqi,ZHANG Zengqi,XU Zongwei.Generation of longitudinally polarized multi-segment optical needles by tightly focusing RPBG beam[J].Optoelectronics Letters,2023,(7):399-404 |
| Generation of longitudinally polarized multi-segment optical needles by tightly focusing RPBG beam |
| Author Name | Affiliation | | SHI Changkun | State Key Laboratory of Precision Measuring Technology & Instruments, Tianjin University, Tianjin 300072, China | | SONG Yiding | School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China | | DONG Bing | State Key Laboratory of Precision Measuring Technology & Instruments, Tianjin University, Tianjin 300072, China | | ZHOU Zhanqi | State Key Laboratory of Precision Measuring Technology & Instruments, Tianjin University, Tianjin 300072, China | | ZHANG Zengqi | State Key Laboratory of Precision Measuring Technology & Instruments, Tianjin University, Tianjin 300072, China | | XU Zongwei | State Key Laboratory of Precision Measuring Technology & Instruments, Tianjin University, Tianjin 300072, China |
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| Abstract: |
| In this paper, an effective method to garner sub-wavelength longitudinally polarized multi-segment optical needle sequence by using a specially designed hybrid filter (HF) in a high numerical aperture (NA) objective focusing system is proposed. The HF is coupled by a binary phase transmission function and a multi-segment modulation function, and the binary phase filter is designed by the particle swarm optimization (PSO) algorithm and acts on the radially polarized Bessel Gaussian (RPBG) beam to obtain a longitudinally polarized optical needle with long depth of focus (DOF, 6λ) and a sub-wavelength transverse spot size (0.430λ). The optical needle is with high uniformity of 98% and high beam quality of 96%, and the negligible sidelobe is 15%. On this basis, the multi-segment optical needle sequence with tunable spacing or number can be realized by the multi-segment modulation function. It is found that the HF makes the generation of multi-segment optical needle sequence more flexible and reliable. This research has broad application prospects in material processing, particle acceleration, particle capture and other fields. |
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