Photonic crystals obtained by the modified Stöber method with the natural sedimentation of nanospheres is investigated. The surfaces of the silica nanospheres are investigated using atomic-force microscopy. The surfaces of all samples have a cauliflower structure. The structure of the photonic crystals is studied by the method of small-angle synchrotron radiation scattering (SASRS). The SASRS curves exhibit two or three regions with different scattering intensities. Three original techniques for analyzing the data obtained are proposed. Periodicity in the dependence of the logarithm of intensity on the scattering vector at the smallest wavenumbers, related to scattering from nanospheres, is found. The influence of the water/TEOS molar ratio on the size and concentration of these particles is revealed. Particles of two types (nanospheres and subglobules) are observed at low water concentrations (6–8 mol/L), whereas at water concentrations of 13–23 mol/L the particles are of three types (nanospheres, subglobules, and grains). The morphology of the detected particles is estimated.

This article provides an overview of the key elements of radars built on the basis on microwave photonics (MPh). The technical solutions currently available on the market for all key nodes of the MPh radar are investigated. The possibility of switching from traditional radars to MPh radars ones is investigated and the advantages of such a transition are substantiated. A study of the appearance of an ultra-wide-band dual-band radar for navigation of ships in the Arctic zone based on elements of MPh has been carried out. The potential tactical and technical characteristics on systems are evaluated, taking into account the work in difficult climatic conditions, a comparative analysis with existing radars is carried out. Modeling has shown that it is possible to increase the detection range and a significant increase in the range resolution, as well as increase noise immunity, which will improve the quality of navigation support.

Photonic crystals based on amorphous SiO2 nanospheres have been obtained in four-component H2O–Si(OC2H5)4–NH3–EtOH systems at a constant initial volume (100 mL), a constant molar ratio of NH3:Si(OC2H5)4 = 10 : 1, and varied molar ratio of H2O–Si(OC2H5)4 (x1) and H2O–EtOH (x2) within the range of 30–110 and 0.4–2.8, respectively. The increase in water concentration and simultaneous decrease in the alcohol concentration in the initial mixture have resulted in the reduction of mean diameter of the SiO2 spheres from 440 to 270 nm. The curves of the correlation curves between effective diameter of the nanospheres– and the H2O–Si(OC2H5)4 and H2O–EtOH molar ratio have shown two regions with different slopes: for the samples obtained at low H2O–Si(OC2H5)4 and H2O–EtOH molar ratios for these obtained at [H2O] : [Si(OC2H5)4] > 50, [H2O] : [EtOH] > 1. Correlations between the size of the nanospheres of oligomerized SiO2, the initial rate of the process, and the dielectric constant of the initial mixture have been found. The spectral parameters of the photonic crystals obtained on the basis of the amorphous SiO2 spheres have been affected by the H2O–Si(OC2H5)4 and H2O–EtOH molar ratios in the initial mixtures.

Technologies for creating microresonators based on the effect «whispering gallery modes» (WGM) and distributed feedback (DFB) lasers used in an optoelectronic generator (OEO) are investigated and generalized. The calculation of the natural frequencies WGM resonator and DFB laser is presented. Software modeling of electromagnetic field distribution in MATLAB environment is implemented. An approach to the manufacturing technology DFB laser with a low-level phase noise based on a photonic crystal (PC) is proposed. The possibility of using this laser and resonator in an optoelectronic system for generating an ultrahigh frequency (UHF) signal to create coherent microwave photonic radars is considered. The advantages of these lasers for creating a single master OEO of promising multi-band radar are shown.

Real-time thermal analysis is used for the synthesis of silica globules. The rate of the reaction of sol synthesis is determined. The reaction order is found, depending on the concentration of water, and the kinetic and diffusion regions are identified. Dried (not annealed) samples are studied via DSC. The dynamics of ethanol and water evolution from the samples is studied in analyzing the heating and cooling curves. Structural phase transformations of the formation of β-cristobalite and its transition to the α-form are observed. The dependence of the amorphousness of the sample on the amount of water in the solid phase is determined. It is found that when the water–TEOS molar ratio is less than fifty, the process proceeds slowly and hydrolysis is incomplete. An explanation of this pattern is proposed. A reaction equation for the kinetic region is determined for the case when the indicated molar ratio is more than 100. A general chemical formula for the main structure of a globule’s core is proposed, with allowance for the presence of cristobalite fragments in all samples. Based on an analysis of this formula, a condition is found for the case when the hexagonal ring cannot be the basis of the structure, and the amount of chemically retained water can be determined. A stoichiometric formula for the product that forms in the diffusion region is obtained.

Methods and principles of stepped frequency signals generation are researched and generalized. Mathematical models of stepped frequency signals are described. Software signal models are implemented to evaluate the possibility of developing a device for probing signals synthesizing. These signals can increase the range resolution of radars. As an example, a schematic calculation of the device for stepped frequency probing signals synthesis is carried out. The possibility of stepped frequency signals generation in the optical wavelength range based on lasers for multi-band radars development is considered. Conclusions are drawn about the possibility of creating advanced multiband radars with a single optoelectronic oscillator.