Gao Binjie, Wen Jisen, Zhu Guiyuan, Ye Linhua, Wang Li-Gang
Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou 310027, China.
Research Center for Intelligent Chips and Devices, Zhejiang Lab, Hangzhou 311121, China.
Nanoscale. 2022 Feb 24;14(8):3123-3130. doi: 10.1039/d1nr06163a.
Fractional vortex beams (FVBs) were believed to be hard to rotate microparticles at a half-integer topological charge due to the unique radial opening (low-intensity gap) in their intensity ring. However, recent research discovered more symmetric intensity structures with less intensity inhomogeneity of practical FVBs at the focal plane. Here, we experimentally demonstrated the manipulation of trapped microparticles and precisely measured their rotation periods at the focal plane of practical FVBs by using a high-speed camera. We verified that the measured orbital angular momentum (OAM) derived from the collective microparticle rotation is roughly proportional to the fractional OAM of practical FVBs. Furthermore, we also experimentally obtained the trapped microparticles' power spectra under the illumination of FVBs, from which we achieved the average trap stiffness to evaluate the two-dimensional trapping strength of the practical focused FVB intensity ring. Our results provide a new insight and an efficient tool on finely trapping and rotating microparticles and bio-cells by using fractional vortex beams.
分数涡旋光束（FVBs）由于其强度环中独特的径向开口（低强度间隙），被认为难以以半整数拓扑电荷旋转微粒。然而，最近的研究发现，实际FVBs在焦平面上具有更对称的强度结构，强度不均匀性更小。在这里，我们通过实验展示了对捕获微粒的操控，并使用高速相机精确测量了它们在实际FVBs焦平面上的旋转周期。我们验证了从集体微粒旋转中导出的测量轨道角动量（OAM）大致与实际FVBs的分数OAM成正比。此外，我们还通过实验获得了FVBs照明下捕获微粒的功率谱，从中我们得到了平均捕获刚度，以评估实际聚焦FVB强度环的二维捕获强度。我们的结果为利用分数涡旋光束精细捕获和旋转微粒及生物细胞提供了新的见解和有效工具。
