Light Focusing and Optical Vortices

Dear Colleagues,

Solving a problem that is as fundamental as controlling the state of light is a one of the most important areas of study in modern optics and nanophotonics. To achieve this goal, it is essential to understand the physical effects that arise during the propagation of laser beams, including during their focusing, as well as the possibility of predicting these effects. This is possible by developing a theory which describes the characteristics of laser light. Singular optics, which studies vortex optical beams, can be called upon to answer these questions. 

Optical vortices are widespread in modern science. The energy in these beams propagates in a spiral in such a way that a "funnel" is formed, which is similar to an air vortex (tornado). Optical vortices were named as such for this reason. The worldwide scientific community is highly involved in the investigation of the formation, propagation, focusing, and detection of optical vortices. Over the past three decades, significant fundamental studies on vortex beams have been carried out, which presented new beam types and optical phenomena in vortex beams. Experimental research has been devoted to different approaches and technologies for the generation of vortex beams and the measurement of orbital angular momentum.

Vortex beams have become one of the most important light sources today because each photon in a vortex beam can carry orbital angular momentum. Therefore, vortex laser beams have been applied in a fairly wide range of fields and have caused the rapid development of optical technologies. They are primarily used to capture and rotate nanoparticles in a circle in the plane of a beam cross section. This property of optical vortices became the basis for the creation of optical tweezers, which made it possible to investigate tiny and complexly organized objects such as, for example, DNA molecules. Optical vortices are also used in optical communications, in quantum computing, in modulation nanolithography and cryptography, etc. In addition to optical vortex beams, some other vortices, such as  electron vortex beams, neutron atom vortex beams, plasmonic vortices, and radio vortices, can lead to new applications in science and technology.

This Special Issue aims to present state-of-the-art articles regarding both theoretical and experimental studies on the generation, propagation, focusing and measurement of light beams and applications of structured beams. Topics include, but are not limited to:

• The design, simulation, and manufacturing of optical devices for light focusing (metasurfaces, zone plates, plasmonic lenses, etc.);
• Properties of tightly focused light;
• Photonic nanojet;
• Light bullet;
• Overcoming the diffraction limit;
• Applications of tightly focused light;
• Singular optics;
• The generation of optical vortices;
• Vortex dynamics;
• Partially coherent vortex beams;
• Fractional vortex beams;
• Plasmonics vortices;
• Cylindrical vector beams;
• Vector vortex beams;
• Orbital angular momentum;
• Spin orbital conversion;
• Applications of vortex beams.

Dr. Elena Kozlova
Guest Editor

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