The experimental study has been carried out using advanced computer vision methods in order to visualize the moment of excitation and further propagation of a non stationary isotropic domain in a hybrid aligned nematic (HAN) microsized volume under the effect of a laser beam focused on a bounding liquid crystal surface. It has been shown that, when the laser power exceeds a certain threshold value, in bulk of the HAN microvolume, an isotropic circular domain is formed. We also observed a structure of alternating concentric rings around the isotropic circular region, which increases with distance from the center of the isotropic domain. The formation of a sequence of rings in a polarizing microscopic image indicates the formation of a complex topology of the director field in the HAN cell under study. The following evolution of the texture can be represented by two modes. Firstly, the “fast” heating mode, which is responsible for the formation and explosive expansion of an isotropic zone in bulk of the HAN microvolume with characteristic time τ1 due to a laser spot heating on the upper indium tin oxide (ITO) layer. Secondly, the “slow” heating mode, when an isotropic zone and concentric rings slowly expand with characteristic time τ2 mainly due to the finite thermoconductivity of ITO layer. When the laser power significantly exceeds the threshold value, damped oscillations of the isotropic domain are observed. We also introduced the metrics that allows quantitatively estimate the behavior of texture observed. The results obtained form an experimental basis for further investigation of thermomechanical force appearing in the LC system with coupled gradients of temperature and director fields.

A method has been proposed for photoinduced hyperthermia of pathogenic Gram-negative bacteria P. aeruginosa using Gd2O3:Yb micropowder. It is based on the possibility of laser excitation of anti-Stokes luminescence on ytterbium ions in the gadolinium oxide micropowder, which allows us, on the one hand, to heat the powder to the required temperature and, on the other hand, to accurately control the powder temperature using remote luminescent thermometry. It has been demonstrated that the long-term irradiation of the Gd2O3:Yb micropowder with 1035-nm nanosecond laser radiation changes the shape of anti-Stokes luminescence spectra associated with micropowder heating in the range from 27 to 63°C. The application of the proposed photoinduced hyperthermia method to a mixture of solutions of the Gd2O3:Yb micropowder and P. aeruginosa bacteria demonstrates a decrease in the bacterial population by 90%.

In the present work, we propose a rapid analysis of the trapped ion dynamics regimes. The Hoeffding’s Independence Test (HIT) mapping technique has been considered as a promising approach for the detection of dynamic regimes. As a model problem, we have applied the proposed method to ion dynamics in an octupole ion trap. We compare the results of HIT mapping with the results of direct calculation of the non-trivial Lyapunov exponent. The HIT mapping result well agree with a Lyapunov exponent mapping. The computational time for plotting the HIT maps was significantly less than the computational time for plotting the Lyapunov exponent maps.

Based on a nonlinear extension of the Ericksen-Leslie theory, taking into account the entropy balance equation, a theoretical study of a thermally excited vortex flow in a microsized hybrid-aligned nematic (HAN) volume was carried out. Analysis of the numerical results show that due to interaction between the gradients of the director field del n and temperature del T , caused by the focused laser radiation, the thermally excited vortical fluid flow is maintained in the bulk of the HAN channel. Calculations have shown that the features of the vortex flow are influenced not only by the direction of the heat flux relative to the bounding surfaces, but also by the orientational defect on these surfaces.

The non-stationary topology of a texture formed in a layer of nematic material under the effect of electrohydrodynamic instabilities is investigated. This was done using methods of spatial frequency, fractal dimensions, and methods for determining the average instantaneous velocity of a features point in the texture. The texture topology was studied on the basis of the texture edge detected using the modified Shen-Castan algorithm. Multi-fractal texture analysis at various scales was performed using box-counting algorithm. The time-dependent sweeping process is characterized by the instant velocity of texture featured points using minimax and iterative algorithms. The study of fractal dimensions allowed us to develop a new approach to the assessment of the typical characteristics of a texture topology as a critical size when a large scale of the topology turns into a small one. It has been shown that the characteristic texture size calculated by classical Fourier analysis well agrees with the result of multi-fractal analysis.

We report the results of a study of laser-induced transparency under the conditions of the optical Stark effect in CdSe nanoplatelets. The induced absorption spectra are measured by the pump-probe technique. Laser-induced transparency is observed due to the transfer of the population of the electron states of the valence band to the conduction band as a result of two-photon optical transitions under the action of pump radiation. The transparency of the medium is maintained for the lifetime of the first excited exciton level, which corresponds to 180 ps. The presence of a hypsochromic shift of the exciton absorption band by 3.1 meV for a pump power density of 39 GW/cm2 with the coincidence of pump and probe pulses due to the optical Stark effect is demonstrated. The results of fundamental studies presented in this paper can find application in the development of new photonic devices for controlling light with light.

We have developed a simple electrodynamic manipulator extension for a commercial fluorescence microscope. This extension allows single charged nano- and microparticles to levitate being isolated in space. The proposed electrodynamic manipulator is based on the linear quadrupole Paul trap. We measured the luminescence spectrum of a single microparticle filled with semiconductor quantum dots to demonstrate the operation process of the electrodynamic manipulator. This paper reveals the manipulator design features and restrictions are imposed by microscopic equipment; the issues of optical spectra recording are also discussed. The electrodynamic manipulator is a cheap and robust tool that can be compatible with any commercial microscopes, and can be easily adapted and modified for various investigation needs.

Here we present an experimental implementation of the fluorescence concatless method for the temperature determination of YAl3(BO3)(4) crystals doped with Yb3+ ions. We have investigated the anti-Stokes fluorescence spectra of the crystal in the 900-1020 nm spectral range. The spectra have been measured while heating the crystal in the temperature range from 290 to 573 K. The increase of crystal temperature results in an enhancement of the relative fluorescence intensity in the short-wavelength region. The linear dependencies obtained can be used as a calibration function for contactless temperature measurements of YAl3(BO3)(4) laser crystals doped with Yb3+ ions.

In the present work, we numerically simulate the dynamics of porous charged microparticles localized in surface radio-frequency trap under atmospheric conditions, taking into account laser irradiation. The dynamic system transition from bistability to states characterized by either one or three stable equilibrium points is revealed. The number of stable equilibrium points and their spatial position appear to depend on the magnitude of the particle gravity and optical pressure. The phase portraits of the particle trajectories are calculated for the each dynamic system state. The obtained results are generalized and discussed from a practical point of view

We have investigated the formation of microparticles-based Coulomb crystals in a linear vertical quadrupole Paul trap with a single end-cap electrode. For the first time, we have described the effect of gravity on Coulomb crystals formation. We have observed a new type of stable Coulomb crystals configuration that we referred to as "Christmas tree-like Coulomb crystals". We have provided numerical simulation and experimental research of the "Christmas tree-like Coulomb crystals" and discussed these structures in the perspective of Science and Art performance.

In this paper, we present the nonlinear damping identification method for the fast and comprehensive study of individual microparticles localized in a quadrupole electrodynamic Paul trap. The measurement procedure is discussed in detail. The size, mass and charge of individual silica microspheres from the studied sample are determined simultaneously and non-destructively. Experimental results agree well with the results of independent microscopic examination and density reference values. The further development of the method are outlined.

Nowadays nanostructures are in demand in various fields from biomedicine to green energy. Photoluminescence (PL) spectral measurements are a powerful tool to study nanomaterials unique physical and optical properties. Most modern spectral approaches are associated with the study of a sample on a substrate or in colloidal solution. In turn, we propose a technique for studying the luminescence of a single object levitating in a quadrupole Paul trap. To verify the technique, we investigate PL spectra of individual trapped charged microcluster of CdSe/ZnS quantum dots. The results obtained open prospects of optical research on single particles isolated from the environment.

We have numerically investigated the dynamics of charged microparticles in a “five-wire” surface radio-frequency trap. The period-doubling bifurcation conditions have been shown to depend on the particle, the trap, and the alternating voltage parameters. For a comprehensive study of the dynamics chaotization through a cascade of period doubling, we have used Fourier analysis of a particle trajectory as well as the calculations of a non-trivial Lyapunov exponent map. We have demonstrated that the period-doubling bifurcation is consistent with a Feigenbaum scenario. A new approach to particle property determination can, thus, be based on observing a period-doubling bifurcation.

We propose a new concept of fractal quasi-Coulomb crystals. We have shown that self-similar quasi-Coulomb crystals can be formed in surface electrodynamic traps with the Cantor Dust electrode configuration. Quasi-Coulomb crystal fractal dimension appears to depend on the electrode parameters. We have identified the conditions for transforming trivial quasi-Coulomb crystals into self-similar crystals and described the features of forming 25 Ca+ self-similar quasi-Coulomb crystals. The local potential well depth and width have been shown to take a discrete value dependent on the distance from the electrode surface. Ions inside the crystals studied possess varied translational secular frequencies. We believe that the extraordinary properties of self-similar quasi-Coulomb crystals may contribute to the new prospects within levitated optomechanics, quantum computing and simulation.

In the present study, we propose a new transparent thin-film ITO surface radio-frequency (RF) trap. Charged hybrid microstructures were localized in the developed ITO trap. We show, analytically and experimentally, that the position of the localization zones in the trapped hybrid structure are stable. The transfer of charged particles between localization zones was studied under the action of gravity-compensating laser radiation. We highlight the advantages of transparent thin-film ITO traps to investigate and manipulate charged particles.

The study of charged particles in radio-frequency (RF) traps is associated with optical response registration. The common issue of optical collection efficiency is caused by the FR trap geometry, which restricts its coupling with optical equipment. To overcome this issue we propose a transparent surface RF traps with Indium Tin Oxide (ITO) thin-film electrodes. ITO sputtering techniques are well known and support deposition on any optical surface. The development of full transparent RF trap is associated with ITO refractive index and optical band gap optimisation while maintaining high electrical conductivity. Here we studied the ITO thin film properties depending on post-annealing temperature. We used the optimal procedure to develop transparent surface RF trap. We demonstrate a stable localization of charged microspheres in the electric field of the developed trap. The proposed approach allows full optical access to trapped charged particle.

In this paper we consider the features of ion trapping in a linear quadrupole Paul trap with circular end-cap electrodes. The quasi-periodic and chaotic regimes of the ion dynamics in the conservative case are shown. The conditions for the transition from the quasi-periodic to the chaotic regime are determined. We present a numerical simulation of the ion dynamics and describe the splitting of the localization region as a function of the ratio of the voltage components on the power and end-cap electrodes.

In the present work a formation of extended orbits of single charged particles in a linear radiofrequency trap under the action of the light pressure force of laser radiation is considered. The conditions for the formation of extended orbits depending on the characteristics of the laser radiation and the object of localization are determined.