It is demonstrated how structured laser beams can be used to implement holographic optical tweezers for trapping and manipulating light-absorbing nano- and microparticles in the air. Two types of structured laser beams are investigated: polygon laser beams and superpositions of the Laguerre–Gauss modes with various carrier frequencies shifted relative to the propagation axis. The polygon laser beams generate arrays of optical bottle-beam traps, and the superpositions of the Laguerre–Gauss modes generate multiple light spots propagating along curved trajectories. The experiments have shown a possibility of optically trapping hundreds and thousands of airborne carbon nanoparticle agglomerations in a cuvette and passively guiding the trapped particles along a curved trajectory. The reported results can be used to develop laser manipulation systems for studying and transporting airborne nano- and microparticles.

We investigate polarization transformations carried out with a refractive bi-conical axicon using the FDTD method. The approach is based on the transformation of a circularly polarized optical beam into an azimuthally polarized beam due to the use of a single refractive element with two conical surfaces. On the inner surface of the element, polarization conversion occurs due to the reflection and refraction of rays at the Brewster angle, while the outer surface operates as a converted beam collimator. The distributions of the components of the electric field vector and the polarization vector at different distances from the optical element are considered as criteria for a successful polarization transformation. By numerical simulation of the performance of a bi-conical axicon made of glass with a refractive index of n = 1.4958, the efficiency of the proposed approach for a circularly polarized Gaussian beam with a wavelength of λ = 1.5 µm is shown. The proposed element is shown to be immune to chromatic aberrations in a significant range of changes in the refractive index of the element material and incident wavelengths (1.5 ≤ n ≤ 1.7; 1 μm ≤ λ ≤ 1.5 μm).

Complex polarization-phase transformations are considered, which are implemented using easy-to-manufacture optical elements. The manufacturing technology of such elements is based on the axially symmetric discretization of the required polarization and phase distributions. This representation leads to optical elements in the form of sector sandwich structures consisting of polarizing and phase plates stacked together. The paper numerically and experimentally investigates the main types of such sector sandwich structures for the formation of second-order cylindrical polarizations.

We investigate the possibility of multi-plane photophoretic trapping of airborne light-absorbing particles using a multi-linear optical trap created with a cylindrical lens. The diffraction of a Gaussian beam on the edge of the lens leads to the generation of a set light lines with decreasing intensities in a transverse plane. Each of the shaped light lines can be used for trapping of different particles because of the photophoretic forces acting on the trapped particles depend on the light intensity. We show that larger particles cannot be trapped by light lines with decreased intensity, while smaller particles can. In addition, initial laser power attenuation leads to intensity fading of the generated non-main light lines and considerable decreasing in trapping robustness which causes to the escape of the smaller particles trapped in these light lines. All these results were experimentally confirmed and can be used for implementation of passive sorting of particles based on their physical properties.

We compare transverse structure evolution and energy deposition into the medium within focused multifilament arrays created using two different types of diffraction optical elements (DOEs): TEM11 phase plate and a Dammann grating. We show that the employment of the Dammann grating provides a robust way to create regular multifilament arrays, which is far less dependent on laser beam quality than one using the phase plate.

A brief review of works devoted to theoretical and experimental studies of structural and polarization transformations of laser beams in anisotropic crystals is presented. Generation of laser beams with a complex polarization-phase state is shown. It is demonstrated that adaptive tuning of structural and polarization-phase states can be carried out by relatively slow changes in the parameters of the optical system and by fast electro-optical modulations with a high response rate.

The propagation of vortex beams of wavelength 1530 nm through an aerosol and turbulent atmosphere was experimentally investigated. The stability of a vortex phase under the beam wandering caused by a flow of warm air was experimentally showed. The results obtained can be used for optical atmospheric communication.

In this paper, we consider a problem of reconstructing complex coefficients of the coherent su-perposition of Laguerre–Gaussian modes from the field intensity in a plane perpendicular to the propagation axis at a given distance using the Levenberg–Marquardt and Brent algorithm. The efficiency of using stage-by-stage optimization to restore complex coefficients of a superposition is demonstrated not only on model, but also on experimental intensity distributions. The algorithm can be used in optical information transmission through a turbulent atmosphere to process the received intensity distribution of the optical signal.

We propose to create radially polarized beam using 8-sectorial polarizer. The manufacturing technology of such elements is based on axially symmetric discretization of the required polarization and phase distributions. This representation leads to optical elements in the form of sector plates Simulation is provided with Comsol multiphysics software. We show that the plate can create the radially polarized beam with the vortex phase.

An optical system for converting linearly polarized laser beams into cylindrical vector beams is developed and experimentally investigated. The scheme is based on the coherent addition of mode beams using a Mach-Zehnder interferometer. The simplicity and versatility of the optical setup is achieved through the use of different sections in the area of the spatial light modulator for the si-multaneous generation of two spatially separated given mode beams. Each of the beams then propagates in one of the arms of the interferometer and undergoes the necessary polarization-phase transformations to obtain a cylindrical vector beam after the addition of mode beams.

We demonstrate a novel approach to create regular multifilament arrays under additional focusing by use of a Dammann grating. The employment of Dammann grating offers an advantage over the Hermite-Gaussian phase plates in terms of multifilament array robustness and resistance to beam imperfections and fluctuations.

Diffraction is a phenomenon related to the wave nature of light and arises when a propagating wave comes across an obstacle. Consequently, the wave can be transformed in amplitude or phase and diffraction occurs. Those parts of the wavefront avoiding an obstacle form a diffraction pattern after interfering with each other. In this review paper, we have discussed the topic of non-diffractive beams, explicitly Bessel beams. Such beams provide some resistance to diffraction and hence are hypothetically a phenomenal alternate to Gaussian beams in several circumstances. Several outstanding applications are coined to Bessel beams and have been employed in commercial applications. We have discussed several hot applications based on these magnificent beams such as optical trapping, material processing, free-space long-distance self-healing beams, optical coherence tomography, superresolution, sharp focusing, polarization transformation, increased depth of focus, birefringence detection based on astigmatic transformed BB and encryption in optical communication. According to our knowledge, each topic presented in this review is justifiably explained.

The possibility of constructing a near-infrared atmospheric optical communication system based on a pair of media converters of a signal format 100Base-TX / 1000BASE-T to format 1000BASE-SX / LX with SFP transceivers DEM-310GT was experimentally investigated. The FAN-OUT TUBING FTB900 SN-Y4 fiber cable connector, coming from the receiving radiation collimator for matching with the DEM-310GT transceiver, was modified. The transmitting radiation collimator is supplemented by a spiral phase plate to form a vortex beam. The influence of atmospheric influence on the data rate is analyzed.

An optical scheme of an interference shaper for polarization-inhomogeneous laser beams is presented. The principle of operation of which is the combined use of an interferometer and an electro-optical light modulator. The advantage of such a shaper is the ability to generate different types of polarizations and different amplitude-phase structure of beams. The applicability of the developed scheme for the formation of an azimuthally polarized beam is shown experimentally.

An interference polarizer for forming a radially-polarized zero-order vortex Bessel beam with the wavelength of 1530 nm has been developed. The polarizer contains 33 layers of SiO2 / Nb2O5 evaporated on a glass substrate using the vacuum electron beam method. The measurement of polarizer characteristics showed the ratio of transmittance of radially- and azimuthally-polarized beams to be 80:1 - 90:1 with the angle of incidence equal to 24.5 - 25 degrees. The transmittance of radially-polarized light was not less than 75%. A radially-polarized zero-order vortex Bessel beam of high optical quality was formed with the help of the developed polarizer and a diffractive axicon.

A new approach is proposed to implement phase contrast Zernike filter with dynamic transparent for phase objects visualization. We investigated the effect of the radius size of the filter at the low and high phase distribution of objects in the input plane to the spatial intensity distribution. A significant increase in contrast is shown when using the proposed dynamic filter. The experimental results of the dynamic phase-contrast filter Zernike are consistent with the numerical simulation.

"We report a detailed study of paraxial Laguerre-Gaussian beams with a zero total angular momentum provided by opposite signs of the vortex phase singularity and circular polarization. These beams are characterized by the multi-ring structure. We have calculated analytically the components of the Umov-Poynting vector and the angular momentum density in the focal region. The local integral characteristics associated with the Umov-Poynting vector and angular momentum density are analyzed. The main attention is paid to the characteristics of the Umov-Poynting vector components in separate rings at different values of the radial index of the Laguerre-Gaussian modes. The multi-ring structure can be used to change the trajectory of the translational rotation of the trapped microparticles. We have shown that the ratio of the local integral angular projection of the Umov-Poynting vector to its longitudinal projection is slowly increases at growth of the radial index.

A completely symmetrical scheme of a shaper of cylindrical vector beams is proposed in which two diffractive axicons and an interference polarizer placed in-between form a sandwich structure of the smallest possible thickness. The design and experimental study of an interference polarizer for generating the radially polarized radiation at a 1530-nm wavelength is carried out. A pair of amplitude diffractive axicons with a period of 3.62 μm to provide the diffraction angle of 24.5° required for generating radial polarization is fabricated. The transformation of a circularly polarized beam into a radially polarized vortex beam is experimentally demonstrated.

Abstract The paper presents the manufacturing technology of a four-sector polarization converter for the formation of beams with different hybrid polarizations. A calcite crystal was used as a transducer, two opposite sectors of which were etched to a depth of 1970 nm. The work is demonstrated and experimental patterns of the total intensity distribution, x-components and y-components in the wavelength range of 500-800 nm for the light transmitted through the transducer and also in the focus distribution are shown. The theoretical and experimental dependence of the degree of conversion is described depending on the parameters of manufacturing the sectors of a four-sector converter. For this purpose, a tunable laser was used in the experiment. The operation of the transducer for the vortex field was simulated.

The paper proposes a method for calculating the phase function of subwavelength diffractive optical elements. The method is based on diffraction gratings with a varying period for generating vector beams with arbitrary-order cylindrical polarization. Formulas for the phase function of the grating are obtained with due regard for the period variation for increasing the efficiency of the polarization conversion of the incident beam. The obtained phase functions are supposed to be used for creating polarization-conversion diffractive optical elements for noise-resistant optical communication systems.