Broadband generation of photonic spin-controlled arbitrary accelerating light beams in the visible
Qingbin Fan, Wenqi Zhu, Yuzhang Liang, Pengcheng Huo, Cheng Zhang, Amit K. Agrawal, Kun Huang, Xiangang Luo, Yanqing Lu, Chengwei Qiu, Henri J. Lezec, Ting Xu
Bending light along arbitrary curvatures is a captivating and popular notion, triggering unprecedented endeavors in achieving quasi-diffraction-free propagation along a curved path in free-space. Much effort has been devoted to achieving this goal in homogeneous space, which solely relies on the transverse acceleration of beam centroid exerted by a beam generator. Here, based on an all-dielectric metasurface, we experimentally report a synthetic strategy of encoding and multiplexing arbitrary acceleration features on a freely propagating light beam, synergized with photonic spin states of light. Independent switching between two arbitrary visible frequency accelerating light beams with distinct acceleration directions and caustic trajectories is achieved. This proof-of-concept recipe demonstrates the strengths of the designed metasurface element: a subwavelength pixel size, independent control over light beam curvature, multi- wavelength operation in the visible, and ultrathin scalable planar architecture. Our results open up the possibility of creating ultra-compact, high-pixel density and flat-profile nanophotonic platforms for efficient generation and dynamical control of structured light beams.