Variable-order perfect vortex beam generation method and tolerance analysis based on metasurfaces.

A perfect vortex beam (PVB) is a wavefront helically structured beam that has the capacity to transport Orbital Angular Momentum (OAM). PVB is typically generated by Bessel Gaussian beams, which can be modulated by phase modulation devices, such as spiral phase plates and SLMs. However, these methods are constrained by the redundancy of the operational devices and the singular order of the beams. This paper presents the design of a passive device that can generate PVB with a continuously variable order, utilizing the metasurface phase control technology and the Moiré lens principle. The device can only accomplish the continuous transformation of 0∼6 order PVB through simple mechanical rotation. Meanwhile, the structure maintains a rotation angle tolerance of -0.4° to +0.6°, the axial misalignment deviation between two metasurfaces can reach 1.5 λ, a beam inclination tolerance of ±3°, and a wavelength deviation tolerance of ±6 nm. This design offers a convenient solution for generating continuously variable-order PVBs and advances the integration of structured-beam optical platforms.