A multifocus optical vortex metalens, with enhanced signal-to-noise ratio, is presented, which focuses three longitudinal vortices with distinct topological charges at different focal planes. The design largely extends the flexibility of tuning the number of vortices and their focal positions for circularly polarized light in a compact device, which provides the convenience for the nanomanipulation of optical vortices.

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Visible-Frequency Metasurface for Structuring and Spatially Multiplexing Optical Vortices.

The first article by Turunen and Friberg deals with a class of fields with propagation-invariant properties such as the optical intensity distribution. Coherent and partially coherent stationary and pulsed solutions are treated in view of scalar and electromagnetic approaches. Approximations of ideal propagation-invariant fields and methods for their generation are discussed. Finally, some application areas are covered.

Propagation-Invariant Optical Fields

Three-dimensional arrays of optical bottle beams

We introduce a new class of nondiffracting fractional vortex beams that connect Bessel beams of successive order in a smooth transition. The new fractional-order beams preserve the same nondiffracting feature of Bessel beams of integer order, and their orbital angular momentum per photon can take any value in a continuous range. The propagation of the more physically realizable fractional-order Bessel–Gauss beams, i.e. fractional Bessel beams apodized by a Gaussian transmittance, through general ABCD optical systems is studied in detail and is complemented by the experimental generation of several instances of fractional beams which in turn confirms our theoretical predictions.

https://iopscience.iop.org/article/10.1088/1464-4258/10/01/015009/pdf

Nondiffracting vortex beams with continuous orbital angular momentum order dependence

Orbital angular momentum of light

Propagation of Bessel beams carrying optical vortices

Self-action of Bessel light beams in medium with large nonlinearity

Nonlinear self-reconstruction of truncated Bessel beam

The vorticity of a free propagating second harmonic (SH) beam produced in a nonlinear quadratic crystal by a combined beam composed of two coaxial Laguerre–Gaussian vortex beams is analysed. In the near field of the SH radiation an aligned vortical structure with a number of double-charge vortices is created. The diffraction of the SH beam under free propagation is also discussed.

K. Regelskis

Papers

Propagation of Bessel beams carrying optical vortices

Self-action of Bessel light beams in medium with large nonlinearity

Nonlinear self-reconstruction of truncated Bessel beam

Free-space propagation of second harmonic Laguerre-Gaussian beams carrying phase singularity

Noncollinear interaction of optical vortices in Kerr nonlinear medium