All-dielectric metasurfaces have exceptional potential for next-generation tunable optical systems, which are promising for applications in sensing, ranging, and imaging. One attractive way to achieve tunability is by infiltrating dielectric metasurfaces with liquid crystals due to the large tunability that can be achieved. Here, we introduce a fully controllable 3D active tuning of dielectric metasurfaces that include liquid crystals, where an external magnetic field effectively controls molecular reorientation. This approach offers new opportunities for realizing dynamically reconfigurable metadevices without the usual limitations imposed by fixed boundary conditions induced by molecular pre-alignment, which cannot be changed.
We demonstrate that a speckle pattern in the spatially coherent laser field transmitted by a diffuser forms a multitude of
three-dimensional bottle-shaped micro-traps. These multiple traps serve as a means for an effective trapping of large
number of air-born absorbing particles. Confinement of up to a few thousand particles in air with a single beam has been
achieved. The ability to capture light-absorbing particles suspended in gases by optical means opens up rich and diverse
practical opportunities, including development of photonic shielding/fencing for environmental protection in
nanotechnology industry and new methods of touch-free air transport of particles and small containers, which may hold
dangerous substances, or viruses and living cells.
Singular optical beams have been studied for many years after the pioneering work where the wave function of the laser radiation is presented as a steady-state solution of the wave equation for a harmonic oscillator. A major step in understanding the nature of singular beams has been made by introducing the concept of the angular momentum of light and analyzing local energy transfer in a vortex beam. It is now well accepted that the orbital angular momentum of light is an intrinsic feature of the optical vortex. However, the orbital angular momentum was always analyzed for travelling modes and the important issue of the orbital angular momentum associated with standing waves still remains open. The main motivation of our work is to reveal the structure of the orbital angular momentum in a standing wave formed by the counter-propagating optical vortices and study its suitability for an optical trapping and guiding. In this work we show that a superposition of two (or more) vortex beams generates a field structure which has a form of a standing wave in both the radial and longitudinal directions, but it is rotating simultaneously along the tangential direction. We demonstrate that then field of this optical vortex structure could be used as an optical trap and simultaneously transfer the angular momentum of the electromagnetic wave to an object inside the area of vortex localisation. We believe this study provides a basis for developing a novel concept of three-dimensional optical traps where vortices could be created in a local volume by a direct transfer of the angular orbital momentum of the electromagnetic wave to trapped objects.
The aim of the given report is experimental and theoretical research of the diffraction of a Gaussian beam by the optical wedges system. It is shown that this system is able to form high-order optical vortices. The effectiveness of system is about 90%. It was shown, that each wedge changes a charge of phase singularity as a result of edge diffraction. The value topological charge of the optical vortex formed after system is defined by the number of wedges in the system. Changing mutual orientation corners of wedges we can select required conditions of the vortex core. It was revealed that the optical vortex appears structurally steady if the comer of mutual orientation of wedges equals α = πn (where n-number of wedges).
Array of fundamental Gaussian beams located on the surface of a hyperboloid of revolution forms a regular net of optical vortices whereas a resulting field represents a singular Bessel-Gaussian beam. A total topological charge of the beam is defined by a phase matching in the beam's array. Such simple key inferences were drawn from our theoretical analysis of light scattering with a stack of optical wedges. We experimentally found out that a Gaussian beam diffracted by a system of dielectrical wedges carried over central-positioned optical vortex, whose topological charge was equal to a number of wedges in the stack.
The high-intensity singular beam turns out to be created by means of the ordinary cover glass for a microscope. For this it is necessary to place the edge of the cover glass into the high-power fundamental laser beam. At the expense of the technical wedging of the cover glass beyond the transparent appears the high-quality singular beam bearing the optical vortex. The given paper represents the physical mechanism of such process illustrated with the vast experimental and theoretical results.
The high-intensity singular beam turns out to be created by means of the ordinary cover glass for a microscope. For this it is necessary to place the edge of the cover glass into the high-power fundamental laser beam. At the expense of the technical wedging of the cover glass beyond the transparent appears the high-quality singular beam bearing the optical vortex. The given paper represents the physical mechanism of such process illustrated with the vast experimental and theoretical results.
The combined singular beams generated by saddle-like imperfections of the cover glass surface in IR spectral range is subjected to the unfolding process near the focal plane of a microobjective. As far as such beams have their intensity profile similar to those of the optical vortices with the quaternary topological charge they can be exploited for the trapping and transportation of large micro particles. In contrast to the ordinary high-order optical vortices being unstable against the slight perturbations of the beam's shape, the given singular beams conserve their topological structure to trap and carry over the particles up to 200 μm in sizes. This fact is discussed in detail in the given work.
It is experimentally and theoretically studied the generated vortex process by the optical wedge and the optical knife. After those optical transparencies it takes place the birth and death vortices events. By adjusting the slope angle of the transparency and the beam truncation depth, the Gaussian beam may be converted into the singular beam transferring a single vortex.
It is considered the construction problems of the fiber- optical sensors of physical values with phase singularities. The signal detection is carried out by the Mach-Zander interferometer with a single-mode fiber as the signal arm and the free propagating singular beam as the reference signal. The sensitivity of such sensor up to 160 rad/( degree(s)C(DOT)m) was achieved.
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