For optical tweezers, a tiny focal spot of the trapping beam is necessary for providing sufficient intensity-gradient force. This condition results in a limited small trapping range to guarantee stable trapping of the particle. Exploiting structured light, i.e., an optical vortex beam, the trapping range can be enlarged by adjusting its doughnut ring diameter. However, the trapped particle scarcely remains static due to the optical spanner action of the orbital angular momentum of the vortex beam. To enlarge the trapping range and simultaneously ensure stable trapping, we propose a beam, referred to as a mirror-symmetric optical vortex beam (MOV). Essentially, MOV is constructed by using two opposite optical spanners and a pair of static optical tweezers. The optical spanners attract the particle to the site of the static optical tweezers, which realizes long-range optical trapping. Through detailed force-field analysis, it is found that MOV could perform these setting functions. In experiments, yeast cells are manipulated in a long range of ∼25 μm, which is 3 times longer than that of the Gaussian beam. Further, the trapping range is easily adjusted by changing a parameter as desired. This technique provides versatile optical tweezers, which will facilitate potential applications for particle manipulation.

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Structured light with more extended degrees of freedom (DoFs) and in higher dimensions is increasingly gaining traction and leading to breakthroughs such as super-resolution imaging, larger-capacity communication, and ultraprecise optical trapping or tweezers. More DoFs for manipulating an object can access more maneuvers and radically increase maneuvering precision, which is of significance in biology and related microscopic detection. However, manipulating particles beyond three-dimensional (3D) spatial manipulation by using current all-optical tweezers technology remains difficult. To overcome this limitation, we theoretically and experimentally present six-dimensional (6D) structured optical tweezers based on tailoring structured light emulating rigid-body mechanics. Our method facilitates the evaluation of the methodology of rigid-body mechanics to synthesize six independent DoFs in a structured optical trapping system, akin to six-axis rigid-body manipulation, including surge, sway, heave, roll, pitch, and yaw. In contrast to previous 3D optical tweezers, our 6D structured optical tweezers significantly improved the flexibility of the path design of complex trajectories, thereby laying the foundation for next-generation functional optical manipulation, assembly, and micromechanics.

Structured light has been exploited as an important tool for particle manipulation along a desired complex path. However, generating the required structured light illumination for the creation of an arbitrary shape without an analytic expression as a guide is challenging, specifically for designing a structured beam by mapping the shape of an arbitrary object. To address this issue, we propose an effective scheme to customize structured light freely and precisely by modifying the epicycle model in astrophysics. Predesigned structured beams can be identified with or without explicit analytic expressions of the desired shapes. Moreover, we study the roles and relationships between the number of epicycles and the number of key points. The local stretching and transformation of a specific structured beam are also analyzed. The advantages of the proposed method are demonstrated by conducting dynamic manipulation experiments using polystyrene particles. This method is simple and intuitive and provides an effective toolkit for the design of structured light for more complex tasks, thus facilitating advanced applications in optical manipulations.

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