We propose a novel and simple method for generating optical vortex with high topological charge (TC), merely using an asymmetrical pinhole plate illuminated by plane wave. N pinholes are arranged along a particular spiral line around the plate origin, with constant azimuth angle increment and varied radial distances. The radial differences introduce a constant variation of m/N wavelength to the optical paths from the N pinholes to the observation plane origin, and this increases the phases of the transmitting waves by progressively $2m\pi /N$and totally$2m\pi$. We numerically calculate the transmitted light field according to the Fresnel diffraction theory, and find the vortex with TC m around the observation plane origin. The experimental verifications are performed using some self-made asymmetrical pinhole plates fabricated by a femtosecond laser, with the high TC vortices both generated and detected in a Mach-Zehnder type interferometer. The experimental results coincide with the theoretical simulations well.

Polarization state of a wave field can be manipulated through the plasmonic metasurface consisting of orthogonal nanoslit pairs; the output polarization angle is independent of the incident linearly polarized light and is highly dependent on the orientations of nanoslit pairs. We combine the Archimedes spiral with the nanoslit pairs to compensate for the Pancharatnam–Berry (PB) phase induced by the orientation of nanoslits, as well as achieve the radially polarized vector beam (RPVB) under the illuminations of different linearly polarized lights. Experiments are performed to successfully realize the RPVB, and the results are in excellent agreement with the numerical simulations.

We propose a method based on six-pinhole interferometers to generate vortex arrays with topological charge 2, only with plane wave illumination. The six-pinhole interferometer is composed of two concentric symmetrical three-pinhole interferometers with different radial distances of the pinholes and a relative rotation of 60 deg from each other. In the Fourier domain, the vortices with second-order topological charge are generated when the radial distances of the two three-pinhole interferometers satisfy some certain ratios. Due to the symmetry of the six-pinhole interferometer, such vortices are distributed at the vertices of some symmetrically distributed regular hexagons. The experimental results obtained in a focal-to-focal system show satisfactory coincidence with the calculations.

A functional metasurface of both transparent medium slices and multiple deflection prisms is proposed, where phase retardations for generating non-diffracting vortex lattices are integrated and encoded as rotation angles of nano-apertures. Under plane-wave illumination, the transmitted waves from the thin flat metasurface act analogously as multiple beams, each with a designed propagating direction and pre-scribed phase shift, that generate an optical lattice within their overlapping region of space. By altering the design parameters of the metasurface, lattice type and size can be controlled. Both numerical simulations and experiments were conducted, verifying the possibility of the proposed method and the non-diffracting properties of the generated vortex lattices.

Vector vortices with spatially varying polarization are interesting phenomena and have motivated many recent studies. A vector vortex in the wavefield of a surface plasmon polariton (SPP) may be extended to the sub-wavelength scale, which would be more significant. However, the formation of vector vortices requires the polarization state to possess components parallel to the surface of metal films. In this study, we generated radially polarized vector plasmonic vortices using the metasurface spiral of orthogonal nanoslit pairs. We theoretically derived the x and y component expressions in the central point area of the spiral and obtained a doughnut-shaped intensity distribution with radial polarization. The Jones matrix of the metasurface spiral was generated to describe the polarization characteristics. The results were validated by performing finite-difference time-domain simulations. In addition, we used a Mach–Zehnder interferometer system to extract the intensity and phase distributions of different components of the SPP field. The experimental doughnut-shaped radially polarized vector vortex was consistent with the theoretical and simulated results.