Constructing ultra-long focal fields via tightly focused Bessel beams
We numerically demonstrate that the tight focusing of Bessel beams can generate focal fields with an ultra-long depth of focus (DOF). The ultra-long focal field can be controlled by appropriately regulating the order of the Bessel function and the polarization. An optical needle and an optical dark channel with nearly
DOF are generated. The optical needle has a DOF of and a super-diffraction-limited focal spot with the size of . The dark channel has a full-width at half-maximum of and a DOF of . Furthermore, the oscillating focal field with an ultra-long DOF can be also generated by merely changing the order of the input Bessel beam. Our results are expected to contribute to potential applications in optical tweezers, atom guidance and capture, and laser processing.
Zhaojin Guo, Mingshuai Huang, Sheng Liu, Peng Li, Bingyan Wei, Jianlin Zhao. Constructing ultra-long focal fields via tightly focused Bessel beams[J]. Chinese Optics Letters, 2023, 21(7): 072601.