This PDF file contains the front matter associated with SPIE Proceedings Volume 11846, including the Title Page, Copyright information, and Table of Contents.

The dynamics of radiation of a two-frequency laser with a vertical cavity is studied by numerical methods. The dependence of the amplitude of the electric field in the stationary regime of laser radiation on the gain is shown.

Numerical model for calculations of spatio-temporal variations of amplitudes of counter-propagating pulses in a standing-wave laser cavity is proposed. Proposed model is based on the transport-type equations for the envelopes of oppositely running pulses, spatial discretization along the cavity axis, and calculation of temporal variations both electric field amplitude and active media polarization/inversion at these points.

The paper presents the results of application of optical system with brightness amplification, a laser monitor, to study the surface of aluminum nanopowder at the time of laser ignition and during combustion. Using a laser monitor, we visualized the presence of a liquid phase in the process of laser ignition of aluminum nanopowder combustion for the first time. For quantitative analysis of the combustion process, we propose using the correlation coefficient of the images of laser monitor. The results of calculating the correlation coefficient demonstrated compliance with the change in the intensity of the images of the laser monitor during combustion and visual observation of the combustion process. For the conventional scheme of a laser monitor with a focal length of 8 cm, the distortions introduced by the instability of the brightness amplifier into the measurement results are estimated. When observing a static test object, the correlation coefficient of the images varied from 0.995 to 0.996, while the fluctuation in the correlation coefficient during combustion is in the range from 0.685 to 0.996, which indicates the possibility of this parameter usage for quantitative analysis of combustion processes in the study using a laser monitor.

Flexible electronics attract great interest due to their wide opportunities for practical application in the field of wireless communication, personalized medicine, security, etc. Flexible wireless technologies require low profile, lightweight, and compact antennas. In this work, an antenna on a flexible dielectric substrate for the ISM range and 2G/3G/4G standards of cellular bands was designed and numerically studied. Also, we plan to fabricate the designed antenna with the help of our original technological approach based on the magnetron sputtering and nanosecond laser ablation. Several preliminary results of microfabrication opportunities with the help of the mentioned above approach are shown.

We theoretically demonstrate a capability of injection-locked semiconductor laser to serve as a nonlinear device for suppression of the amplitude disturbances in a phase-modulated optical signal and significant BER improvement in DPSK optical communications.

Scalable and cost-effective microfabrication approaches are highly demanded for manufacturing of RF and millimeterwave circuits such as transmission structures for flexible electronic devices. Flexible electronics play a key role in wearable and wireless technologies applicable in personalized medicine, sensing, energy harvesting, and communication areas. Here we report the results of thin copper films patterns micromachining using nanosecond-pulsed laser on flexible dielectric substrates. Thin copper films were deposited by magnetron sputtering onto 100 μm thick polyimide films that were used as dielectric substrates. Then, patterns were created through film ablation using a CNC laser micromachining system with a 1064 nm ytterbium 8 ns pulse duration fiber laser to chisel away the superfluous material just as it have been done in sculputure for ages. Several regimes of laser micromachining were studied. The most important issue in the laser micromachining of the metal films on the flexible dielectric substrate is flexible substrate thermal damage due to overheating. Optimal regimes of laser micromachining were found that allow to prevent this. These regimes will be used in the future to fabricate flexible transmission lines for RF and millimeter-wave signals. The schematic and design of the transmission line are considered. Results of numerical simulations made by ANSYS HFSS are presented.

The work investigates the space-time dynamics of semiconductor broad-area lasers with injection of external optical radiation and taking into account the broadening factor of the laser spectral line (alpha factor). It is shown that a nonzero alpha factor leads to modulation transverse instability, which leads to filamentation of laser radiation. It is shown that the injection of external optical radiation suppresses modulation instability and makes it possible to achieve stable spatially uniform paraxial lasing.

The paper investigates a model of a solid-state laser with optoelectronic feedback, which controls the Q-factor of the resonator. It is shown that, with an increase in the feedback response delay time, the transition of laser generation to dynamic chaos is initially observed. Then, with an even longer delay time, rare high-intensity laser pulses appear, called rogue waves. In addition, it was shown that it is possible to deliberately excite such rogue waves using a short-term external action on the system.

In recent decades, there has been a steady trend towards the miniaturization of electronic devices, and their key components. Fabrication of such microsized devices and their key part is a real challenge. One of the well-known methods of microfabrication is laser ablation based micromachining. In this work, we study the peculiarities of the influence of nanosecond laser pulses on thin copper films on dielectric substrates. The main aim of this work is to reveal the effective regime of nanosecond ablation of the copper thin film with different thicknesses. The deposition of a copper thin film on the dielectric substrate was carried out by magnetron sputtering. Glass slides were used as dielectric substrates. To quantitatively describe the interaction of a thin copper film with laser pulses of nanoseconds duration, the fluence was calculated taking into account the velocity of the laser spot. The threshold of fluence that needs to effectively ablate the rectangular region of the copper film with a certain thickness was revealed. The obtained results will be used in the future in precision microfabrication of planar electromagnetic structures for vacuum electron devices operating in millimeter-wave bands.

A multilayer two-dimensional periodic metasurface made of graphene micro-ribbons, which absorbs almost 100% of the energy incident on it at the resonance of the surface plasmon-polariton, has been theoretically investigated. To increase the bandwidth of the device, it is proposed to place 2-3 parallel graphene ribbons with close lengths in one elementary cell of the metasurface. It is shown that at resonance frequencies the generated power of the third harmonic increases by several orders of magnitude and can be increased in comparison with single-layer structures with an increase in the number of layers and packing density of graphene microribbon arrays and when using multilayer substrates.

Non-linear optical properties of titanium nitride nanoparticles were examined using the modified z-scan technique with simultaneous acquisition of the Rayleigh scattering at the direct angle to the polarization plane of a probe laser beam. The real and imaginary parts of the effective dielectric function of nanoparticles, depending on the pump intensity, at the wavelength of 355 nm and the laser pulse energy of 5.8 mJ were reconstructed from the obtained experimental data and displayed using the Cole-Cole diagram technique.

Photo-conductance of quasi-2D layers of molybdenum disilicide nanoparticles was studied under pulse-periodic laser pumping in the spectral range from 355 nm to 480 nm. The layers were prepared using deposition of the nanoparticles from the water suspensions onto the interdigital electrode systems. The influence of the temperature on the photoconductance is examined.

The volumetric anisotropic microlattices, all-optically integrated into different compound materials, are interesting for investigations since they are potentially perspective for optical micro- and nanoelectronic technologies. In this paper the peculiarities of the properties of the volumetric anisotropic microlattices in different compound materials are considered and the comparisons of the nonlinear processes of light-beams transformations in dependence on the concentrations of different chemical elements in investigated bulk samples are discussed.

The results on the low-frequency photo-conductivity of the thin randomly inhomogeneous WO₃ layers are presented. The layers were formed using deposition of water-suspended WO₃ micro-particles onto the glass substrates with flat interdigital electrode systems. The wavelength-dependent photo-conductivity was analyzed in the spectral interval covering the edge of the fundamental absorption band (from 440 nm to 520 nm). The estimated Urbach energy of the examined system occurred equal to ≈ 0.13 eV at 308 K.

The plasmon-assisted photoconductive antenna-emitter has been developed, optimized, and fabricated on a semi-insulating GaAs photoconductive substrate. Using numerical simulation, we showed that a high aspect-ratio of the antenna plasmonic electrodes h/p = 0.5 (where h and p are height and period of metal grating, respectively) can substantially increase the amplitude of the electric field at the shadow side of the grating leading a robust localization of photocarriers in vicinity to plasmonic electrodes. The plasmonic PCA-emitter exhibits 10 μW of the emitted THz power at optical pump of 10 mW, high thermal (breakdown) stability, and the increased dynamic range, as well.

Gain saturation effect in the cavity with hyperbolic graphene medium is investigated. THz wave emission in the cavity was investigated numerically using transfer matrix method. It was assumed that the gain saturation appears as the decrease of imaginary part of effective dielectric permittivity. The intensity of THz radiation and the frequencies of oscillations have been calculated using recursive procedure.

Nanocomposite materials based on noble metal nanoparticles have recently attracted the interest of both researchers and engineers. The reason lies in the unique optical properties of such materials. Thanks to nanoparticles with a pronounced frequency dependence of the dielectric constant, the nanocomposite of such particles in a dielectric matrix acquires the properties of a resonant medium. In such a medium, collective excitations such as bulk and surface polaritons are possible. For a model of a nanocomposite, consisting of nanoparticles of noble metals, uniformly distributed in a dielectric matrix, the dielectric constant is plotted. The analysis of ellipsometric parameters at reflection from the nanocomposite of a wave of linear polarization is carried out.

A model is proposed for calculating the Casimir-Lifshitz force between two finite rectangular and infinite graphene sheets in a vacuum, based on the classical electrodynamic Green’s function method and two-dimensional conductivity model. The force is calculated using the Maxwell’s tension tensor by solving the integral equations in the spectral spacefrequency domain. It is shown that its origin is due to random vibrations associated with long-wave surface plasmons.

The problems of passing and tunneling a plane electromagnetic wave through a dielectric layer and two dielectric layers separated by a vacuum gap are considered. It is shown that there are no superluminal motions, and the transit time is always longer when passing at the speed of light.

The possibility for creation of the optical anisotropy with small periodicities up to nano-scale in amorphous materials is perspective in future for obtaining of different miniature elements for optoelectronics. In this paper the investigation results of the impact of rare-earth doping upon the process of the creation and also on the properties of the photo-induced micro-periodical anisotropy in different samples are presented. The influence of the variations of the chemical rare-earth components is analyzed and the physical mechanisms are discussed.

Millimeter-band traveling-wave tubes with multiple electron beams have attracted an increasing interest thanks to higher output power. In this work, we report the results of the development of the technological approach to microfabrication of a meander-line slow-wave structure for millimeter-band traveling-wave tubes with multiple sheet electron beams. We used a precision CNC laser machine equipped with a 1064-nm pulsed YAG:Nd fiber laser maintaining regimes with the duration of laser pulses from 200 ns to 8 ns. Several SWS samples have been fabricated and studied by scanning electron and optical microscopy methods

We investigate laser manipulation of airborne light-absorbing particles trapped by two-dimensional Airy beams (AiBs). The unique properties of these beams, namely propagation along accelerating trajectories and self-healing allowed us to demonstrate the possibility of trapped particles to bend around obstacles. Previously, only straight-forward propagating laser beams were used for the laser guiding of airborne light-absorbing particles. For example, Gaussian, optical vortices, or conical beams. Such straight-forward propagating laser beams can only push or pull the trapped particles along the straight trajectories, thereby limiting the use of laser beams to cases of the manipulation of the particles which are in a line of sight. In this article, the trajectories of the particles trapped using a straight-forward propagating Bessel beam and AiB were compared and the experiments showed the possibility of using AiBs to guide particles in both directions from and toward the laser source depending on the parameters of the trapped particles. We believe that the use of AiBs can significantly expand the use of photophoresis-based laser manipulation and will allow the non-touch trapping and delivery of light-absorbing particles from various reservoirs and areas of space that are "around the corner" and hidden by an obstacle in the air.

We investigate the diffraction of a polarized light by nonlinear spiral phase plate (NSPP) in the near zone, taking into account the three-dimensional structure of the optical element. The simulation of the NSPP diffraction is based on the finite difference time domain (FDTD) method. The results of numerical simulation of the NSPP diffraction for both homogeneous (linear and circular) and inhomogeneous (radial and azimuthal) polarized light are presented.

Numerical simulations of signal formation in optical coherence tomography (OCT) is a useful tool for understanding and evaluation of the actively developing novel modalities in OCT including, but not limited to elastography, angiography and high-resolution OCT-imaging based on digital refocusing. Numerical simulation of OCT signals allows one to simulate OCT scans using highly controllable parameters characterizing the tissue, e.g., position of the scatterers, their scattering properties, evolution of the scatterer positions (due to straining, Brownian motions or flows). In real or physical phantom experiments sufficiently fine control of these parameters is very complicated or even impossible, therefore the numerical simulations are preferable. We developed a full-wave model for simulations of OCT scans taking into account beam focusing/defocusing and motion of scatterers. This full-wave model can be used for studying OCT signal formation and its analysis in phase-sensitive OCT. Here we present an example of such a computational study of OCT-based angiography with numerical refocusing.

A beam of arbitrary structure is represented as a set of plane monochromatic waves using the Fourier transform. Each of the plane waves falls obliquely in an arbitrary plane of incidence, in such a way that all projections of its wave vector are not equal to zero. The reflection and transmission matrices are obtained for a plane electromagnetic wave incident from an isotropic medium onto a plane inhomogeneous anisotropic layer located on an isotropic base. The found matrices are used to calculate the reflected and transmitted beams.

A method for evaluating the viscosity of turbid biological fluids and pharmaceuticals is described. The proposed method is based on digital analysis of optical coherence tomography (OCT) raw data. The scanning probe of the OCT-system is positioned perpendicular, a drop of a tested liquid is applied to a scanning probe of the system, so that it hangs freely from its surface under the action of surface tension and gravity. Then, a movable glass slide touches the lower part of the drop ensuring minimal contact. In a correct experiment, the contact area of the upper side (base) of the drop with the solid surface of the scanning probe should be many times larger than the contact area of the lower side of the drop with the movable glass slide. The first three-dimensional structural OCT-image (C-scan) is obtained in the above-described position. The movable slide is driven in perpendicular direction to the scanning probe. A series of three-dimensional structural OCT-images of a deformed drop is acquired during the slide displacement. The deforming surface area is calculated as the area of the corresponding segment of the first C-scan. The magnitude of the deforming force for different moments is calculated based on the characteristics of the controlled motion of the movable plate. The ratio of the deforming force to the area of the deforming surface allows estimating the shear stress at the corresponding moments of time. The shear rate is estimated from the displacement C-scan control points of the drop surface for the known time periods of each deforming step. The dynamic viscosity is estimated by the classical formula, as the ratio of shear stress to shear rate. The results are digitally processed, averaged, are to be used in dynamic viscosity determination and presented to the end user.

The analysis of the parameters of the polarization of laser radiation upon reflection from a plate of a uniaxial crystal showed that such a plate can convert the polarization of the incident radiation. As the latter, we used circularly polarized laser radiation at a wavelength of λ = 0.64 μm. With a change in the angle of incidence of radiation, the reflected polarization changed from circularly polarized to elliptical. In this case, the tilt angle of the major semiaxis of the polarization ellipse changed from negative to positive values. The direction of rotation of the field vector also changed from right circular to left elliptical, passing through linear polarization. An increase in the thickness of the anisotropic plate intensified the effect of wave interference in it - all changes in the polarization parameters with a change in the angle of incidence of radiation occurred more often than with a thinner plate. The analysis of ellipsometric parameters is carried out when circularly polarized laser radiation is incident on an anisotropic plate and the angular spectra of these parameters are obtained when light is reflected from the plate. The results obtained can be used to design polarization converters based on an anisotropic plate.

The paper considers the cross-sectional method and the small parameter method in application to the numerical solution of the problem of single-mode propagation of TE-modes in a smoothly irregular integrated optical waveguide invariant in the transverse direction. The cross-sectional method is formulated as a Helmholtz problem for a two-dimensional strip of smoothly irregular thickness. Using the Kantorovich method, the problem is reduced to a parametric problem for eigenvalues and eigenfunctions on a segment. The small parameter method is formulated as a Helmholtz problem on a two-dimensional plane, which in turn is also reduced to a parametric eigenvalue/eigenfunction problem on an axis. We implement various algorithms for the numerical solution of the resulting problems. Their coincidence high accuracy is shown with at the intersection of the definition domains.

The results of a theoretical study of the evolution of powerful elliptically polarized probe nanosecond pulses of electromagnetically induced transparency are presented. The analysis was carried out for the Ʌ-scheme of inhomogeneously broadened quantum transitions between degenerate levels of the ²⁰⁸Pb isotope. The cases of resonance and quasiresonance are considered under the assumption that the input probe and control radiation have no phase modulation. It is shown that at a higher power of the input probe radiation, the pulses, into which it decays in the medium, are not pulses of normal modes, but their polarization characteristics fluctuate around the values inherent in normal modes, arising at a weak input probe radiation. In the case of a powerful input probe pulse, the phase modulation of the probe field is present at all stages of its propagation in the medium. It is shown that with an increase in the intensity of the input probe radiation, the transparency of the medium for the probe field decreases. However, it is large enough if the polarization characteristics of the input probe radiation coincide with those for normal modes of the parallel type.

An algorithm for modeling light transfer within a complex two-phase foam-like structure using the Monte Carlo simulations is presented. At different stages of aging, gas bubbles in the foam-like medium were presented as Kelvin cells. A tree-dimensional structure was considered as a system of closely packed ordered tetradecahedrons, which are similar in shape to the truncated octahedra with a slight rounding of the walls to satisfy the Plateau rule. The spherical shape of the cells describes the gas bubbles at the early stages, when the foam is wet. In contrast, the polyhedron shape describes the gas bubbles when the foam is dry. Transmittance coefficients of a two-phase foam-like medium for the various radii of the gas bubbles are calculated using the Monte Carlo modeling. Development of such theoretical approach to diagnose the foam structure diagnostic allows for the optimization of synthesis of highly porous materials with the required properties, particularly applying the gas-based and supercritical techniques. This study can be useful for the development of biomedical technologies, especially for the tasks of synthesizing cellular scaffolds.

In this paper, we investigated the entanglement dynamics between two superconducting qubits interacting with a thermal one-mode field of lossless cavity with the Kerr media. We obtained the exact solution for time- dependent density matrix and calculated on its basis the qubi-qubit entanglement parameter-negativity. The results show that Kerr nonlinearity greatly affected the entanglement behaviour. More interestingly, that initial qubits coherence greatly enhances the degree of entanglement in the presence of the Kerr medium.

In this paper, we investigate entanglement between two qubits when they simultaneously not-resonantly interact with a single-mode thermal field through the degenerate two-photon transitions. We obtain the exact solution of the quantum Liouville equation for density matrix of the considered systems in the "dressed" states representation. On its basis the calculate the qubit-qubit reduced density matrix and negativity. We show that a slight detuning between the qubit transition frequency and the twice field frequency might cause high entanglement between the qubits.

The calculations of vibration-rotation bound states and new metastable states of a diatomic beryllium molecule important for laser spectroscopy are presented. The problem is solved using the potential curve and the authors' software package that implements the iteration Newton method and the high-accuracy finite element method. The efficiency of the proposed approach is demonstrated by calculating vibration-rotation bound states and, for the first time, rotation-vibration metastable states with complex- valued energy eigenvalues (with negative imaginary parts of the order of (10^-20 ÷ 6) cm^-1) in a diatomic beryllium molecule. The existence of these metastable states is confirmed by calculating the corresponding scattering states with real-values resonance energies.

For the first time we study the stability of the lanthanide complexes with polydentate hyterocyclic phosphine oxides. Here we report the influence of the structure of phenanthroline (PhenPPO) and 2,2’-bipyridine (DPPO) phosphine oxides on the stability of their lanthanide complexes. An increase in the flexibility of the phosphine oxide structure leads to an increase in the stability of the complexes. The maximum of stability of the complexes is observed on neodymium ion, regardless of the structure of the ligands DPPO and PhenPPO.

In order to interpret the experimental spectrum of phenylalanine measured in the gas phase at a temperature of 520 K, the vibrational spectra of three conformers of phenylalanine were calculated in the harmonic and anharmonic approximations. It was shown that the vibrational IR spectrum of phenylalanine in the gas phase is a superposition of the vibrational spectra of the conformers Phe1 (~50%), Phe2 (~35%), and Phe3 (~15%).

For many methods of optical spectroscopy, there is no analytical and/or direct numerical solution for the problem of determination of concentrations of each component in multi-component solutions by spectra. Therefore, recently, the application of machine learning methods to solve these spectroscopic inverse problems (IP) has been actively investigated. In our previous studies, it was suggested to use an ensemble of optical spectroscopy methods to increase the accuracy of the solution obtained by machine learning methods. Joint use of Raman spectroscopy and optical absorption spectroscopy methods to determine the concentrations of heavy metal ions in water using neural networks was considered. In this paper, we investigate the resilience of the considered IP to noise in data. The task was set to find out whether the joint use of these two types of spectroscopy can improve resilience of the solution to noise in input data of the considered IP in comparison with the case of using each of these types of spectroscopy separately. As possible alternative ways to increase the resilience of the neural network solution of this problem, the previously studied methods of group determination of parameters were considered. The main result is similar to that of the previous studies: combination of a “strong” method with a much “weaker” one does not allow one to increase the results of the “strong” method alone. This regards not only the error of the IP solution, but also its resilience to noise in the input data.

Here we report the investigation of complexation between lanthanide ions nitrates and 4,7-dichloro-1,10-phenanthroline- 2,9-dicarboxamide by spectrophoitometric titration technique. In all studied systems, one complex species is formed with a metal-ligand stoichiometry of 1:1. The stability of the corresponding complexes are strongly depends on the metal ion radius. All of the complexes under the study have high stability, Lu and Gd complexes possesses lgβ more than 6 and Ho and Eu – more than 7.

The paper presents the results of a study of the effect of carbon dots synthesized by the hydrothermal method on the strength of hydrogen bonds in water. For the first time, using Raman spectroscopy and genetic algorithms, the values of the change of the enthalpy of hydrogen bonds were obtained when carbon dots were suspended in water. According to the calculations, the energy of hydrogen bonds in water is equal to 15.5±0.2 kJ/mol, and in an aqueous suspension of carbon dots, it is 14.8±0.2 kJ/mol. The results obtained make it possible to assess the safety of the studied carbon dots as biomedical nanoagents from the point of view of the effect on hydrogen bonds in biological tissue.

Problems of indirect measurements arising in experimental science belong to the class of inverse problems (IP), which are often ill-posed, non-linear, and have high dimensionality. Machine learning methods are used to solve IP due to their ability to resist these unfavorable properties. In this study, we solve an IP of determination of concentrations of components in multi-component solutions by their Raman spectra. The results demonstrated by various machine learning methods are compared by the solution error and by their resilience to various types of noise encountered in experimental spectroscopy. The best results were demonstrated by multi-layer perceptrons with two hidden layers and by convolutional neural networks with one convolutional layer. For multiplicative noise with high noise level, the most noise resilient algorithms were random forest and gradient boosting.

The luminescent properties of two water-soluble europium complexes and two organo-soluble terbium and europium complexes with ligands based on different N-heterocyclic ligands in various mixed solvents (light and heavy water, glycerol, methanol and ethanol) were studied in this work. The absorption, emission, and excitation luminescence spectra were obtained and analyzed. We calculated the asymmetry coefficient, the luminescence quantum yield, and the luminescence lifetime at various concentrations of mixed solvents. The luminescence quenching was found more noticeable in methanol than in ethanol for all studied complexes. We observed that the luminescence quantum yield in the water-containing solvents (methanol/water, methanol/heavy water, ethanol/heavy water) is almost independent of the water or heavy water concentration. We received that heavy water has less influence on luminescence quenching than water, since the vibrational frequencies of OH groups are higher than that of OD groups. Luminescence quenching by adding glycerol to the solvent is more effective for the studied organo-soluble complexes than for water-soluble ones. This effect can be explained by the fact that the ligand of organo-soluble complexes surrounds the rare earth ion more closely, thus preventing glycerol OH groups from entering the coordination zone of the ligand.

We have investigated the effect of doping a graphene matrix with silicon atoms on the structure, vibrational and electronic spectra. The impact of substitution on the shape and intensity of the D line in the RAMAN spectrum is shown. It is demonstrated that the shape of the doped sheet depends on the location of Si atoms, which can lead to a significant increase in its dipole moment.

Silver sulfide nanoparticles is a promising material for biophysics, medicine and nanoelectronics. In present work molecular mechanisms of these nanoparticles bacterial synthesis are studied using quantum chemical modeling methods. The peculiarity of obtaining silver sulfide nanoparticles by biosynthesis using bacteria Bacillus subtilis 168 is that the only flagellin protein involved in the synthesis process and adsorbed on the surface of the particles. Investigated objects are salts-silver nitrate AgNO₃ and sodium thiosulfate Na₂S₂O₃, which are involved in the synthesis process, and nonstandard amino acid methyllysine as a part of flagellin. The study was based on of molecular structures and IR spectra calculation using Density Functional Theory (DFT) methods with B3LYP functional by the Gaussian 09 software package and on analysis of formed hydrogen bonds parameters. It was discovered that methyllysine forms a sufficiently stable molecular complexes with silver nitrate and sodium thiosulfate. This makes it possible to talk about the significant role of methyllysine in the formation of silver sulfide nanoparticles and clarifies the mechanism of its functioning as a part of flagellin.