An overview of the recent developments in the field of cylindrical vector beams is
provided. As one class of spatially variant polarization, cylindrical vector beams
are the axially symmetric beam solution to the full vector electromagnetic wave
equation. These beams can be generated via different active and passive methods.
Techniques for manipulating these beams while maintaining the polarization symmetry
have also been developed. Their special polarization symmetry gives rise to unique
high-numerical-aperture focusing properties that find important applications in
nanoscale optical imaging and manipulation. The prospects for cylindrical vector
beams and their applications in other fields are also briefly discussed.

Cylindrical vector beams: from mathematical concepts to applications

Cylindrical-vector beams are of increasing recent interest for their role in novel laser resonators and their applications to electron acceleration and scanning microscopy. In this paper, we calculate cylindrical-vector fields, near the focal region of an aplanatic lens, and briefly discuss some applications. We show that, in the particular case of a tightly focused, radially polarized beam, the polarization shows large inhomogeneities in the focal region, while the azimuthally polarized beam is purely transverse even at very high numerical apertures.

Focusing of high numerical aperture cylindrical-vector beams.

Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.

/pdf/roadmap-on-structured-light-3r840pnxka.pdf

Roadmap on structured light

▪ Abstract The formation of switchable holographic gratings from polymer-dispersed liquid crystals (H-PDLCs) allows for the development of switchable transmissive and reflective diffractive optics. These structures are created by the coherent interference of laser radiation within a syrup containing photoreactive monomer, initiator, and liquid crystal. Local differences in photopolymerization rates induce phase separation of discrete LC domains to occur periodically commensurate with the period of the interference pattern. These spatially periodic gratings of nano-scale sized LC domains can be formed on grating length scales ranging from 100 nm to microns depending on the optics of fabrication. True Bragg gratings are formed with spacings typically less than 1 μm. Owing to the refractive profile generated by this periodic two-phase structure, diffraction of light occurs. Electrical switching of the average director orientation within the LC domains results in a modulation of diffracted radiation. This tec...

Holographic Polymer-Dispersed Liquid Crystals (H-PDLCs)1

We report a focus shaping technique using generalized cylindrical vector beams. A generalized cylindrical vector beam can be decomposed into radially polarized and azimuthally polarized components. Such a generalized cylindrical beam can be generated from a radially polarized or an azimuthally polarized light using a two-half-wave-plate polarization rotator. The intensity pattern at the focus can be tailored by appropriately adjusting the rotation angle. Peak-centered, donut and flattop focal shapes can be obtained using this technique.

Focus shaping using cylindrical vector beams

Novel liquid-crystal devices are described that generate linearly polarized light with axial symmetry; the beam propagation axis is the symmetry axis. Such light fields can be characterized by a polarization order number P. For example, P = 1 fields represent radially or azimuthally polarized light. The reorientation of the polarization orientation in these polarization converters is due to the twisted nematic effect and the effect of lambda/2 wave plates. A single polarization converter can generate fields of orders 1 and 2. It is shown that one can in principle generate fields of any integral order P by cascading such elements. Devices that generate P = 1 fields are achromatic and can be used as polarization axis finders or as versatile tools for studying birefringent or polarizing materials.

Linearly polarized light with axial symmetry generated by liquid-crystal polarization converters

An electrically switchable diffractive optical element has been built based on a computer-generated phase hologram and a liquid-crystal layer. The design of the diffractive optical element and the fabrication and performance of the device are discussed. The application of the device in a machine vision system for optical surface inspection is shown.

/pdf/electrically-switchable-diffractive-optical-element-for-2puf8m7vn3.pdf

M. Stalder

Papers

Linearly polarized light with axial symmetry generated by liquid-crystal polarization converters

Electrically switchable diffractive optical element for image processing.