Opt Lett. 2023 Jan 15;48(2):469-472. doi: 10.1364/OL.476985.
Metasurfaces for wavefront shaping rely on local phase modulation in subwavelength unit cells, which show limited degree of freedom in dealing with complex and multiple beam transformation. Here, we assign multiple beams into different diffraction orders coaxially located along the same direction, whose wavefronts are tailored by optimizing the diffraction coefficients in two orders and two polarization states of a supercell. By evenly splitting the energy into two orders and adjusting the zeroth-order diffraction phase, a Bessel beam and a vortex beam are simultaneously generated in the near field and far field along a coaxial direction. The effectiveness of the method is validated by the excellent agreement between the simulation and experimental characterization of the two beams.
用于波前整形的超表面依赖于亚波长单元中的局部相位调制，但在处理复杂的多光束变换方面，其自由度有限。在这里，我们将多个光束分配到沿着同一方向同轴定位的不同衍射级中，通过优化超单元的两个阶和两个偏振态的衍射系数来调整这些光束的波前。通过将能量均匀地分成两个阶，并调整零阶衍射相位，可以在同轴方向上的近场和远场中同时产生贝塞尔光束和涡旋光束。该方法的有效性通过对这两种光束的模拟和实验特性之间的良好一致性进行了验证。
