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Nanocrystalline compounds LiNb1−xTaxO3 of various compositions (x = 0, 0.25, 0.5, 0.75, 1) were synthesized by high-energy ball milling of the initial materials (Li2CO3, Nb2O5, Ta2O5) and subsequent high-temperature annealing of the resulting powders. Data on the phase composition of the nanopowders were obtained by X-ray diffraction methods, and the dependence of the structural parameters of LiNb1−xTaxO3 compounds on the value of x was established. As a result of the experiments, the optimal parameters of the milling and annealing runs were determined, which made it possible to obtain single-phase compounds. The Raman scattering spectra of LiNb1−xTaxO3 compounds (x = 0, 0.25, 0.5, 0.75, 1) have been investigated. Preliminary experiments have been carried out to study the temperature dependences of their electrical conductivity.

The electronic receivers of global navigation satellite systems (GNSSs) are implemented in various handheld electronic devices such as laptops, smartphones, and smartwatches; therefore, their dimensions are of critical importance. Achieving a GNSS terminal of a small size is difficult due to its relatively low operational frequency (L-band), which is equivalent to a wavelength of approximately 24 cm. As an efficient half-wavelength antenna is too large for compact devices, in this paper, an electrically small antenna (ESA) for GNSS terminals is presented. The antenna was miniaturized by using a dielectric block with relatively high permittivity, making some parts virtual, and optimizing its geometry. The operational frequency of the ESA is tunable by means of metallic rods of variable heights inserted into a cylindrical cavity drilled inside the dielectric block. The results confirm the feasibility of the concept and the usability of the ESA for compact GNSS terminals.

A concept of electrically small antenna for BeiDou BD2 B3 Chinese navigation satellite system was developed and studied. Three main miniaturized techniques: antenna loading by using high permittivity materials, making some part of antennas virtual by using ground planes and short circuits, and optimizing geometry have been employed in the design. Antenna performance was examined by experiments giving very promising results.

In this paper the results of full-wave electromagnetic modeling of RF transducer for acousto-optic modulator are presented. They show that inclusion only the electromagnetic properties for designing the optoelectronic devices is not satisfying. For this reason, designing process of the optimal (from the acousto-optic point of view) construction of the modulator with RF transducer should include two stages. The first stage has to be based on the acousto-optic requirements. The second stage has to be related to the optimization of the electromagnetic parameters taking into account the results of the first stage.

Bismuth silicon oxide (Bi12SiO20, BSO) is a material having wide range of applications in optical technology, electronics, and microwave techniques. An application in sub-THz devices is also prospective. In view of the foregoing, the electrical parameters of a single-crystal BSO were examined in this work in the 220–325 GHz frequency range. The influence of UV radiation on the transmission of waves through the material was also subjected to an experimental study. The results can contribute to the development of future BSO based sub-THz devices.

In the present work the third-order nonlinear optical (NLO) properties of the complex-oxides crystals, including nonlinear absorption (NLA) and nonlinear refraction (NLR) are performed by the Z-scan technique. The non-centrosymmetric lithium niobate (LiNbO3) and lithium tantalite (LiTaO3) and centrosymmetric cadmium tungstate (CdWO4), calcium tungstate (CaWO4) and calcium molybdate (CaMoO4) single crystals were used for experimental investigation. The main nonlinear optical parameters, such as the two-photon absorption coefficient β, the nonlinear refractive index n2 and third-order nonlinear susceptibility for all investigated crystals are evaluated at different wavelengths λ: 1064 nm and 532 nm. Herein, the influence of λ and crystal orientation of third-order NLO properties on complex-oxides crystals is discussed.

The work presents experimental results of an in situ investigation of optical absorption of LiNbO(3) : MgO during reducing (95%Ar + 5%H(2)) and oxidizing (O(2)) high-temperature treatments in the temperature range from room temperature to 1073 K. The absorption spectra measured at in situ conditions at high temperatures in reducing/oxidizing atmospheres as well as the kinetics recorded at fixed wavelengths during rapid replacement of gas atmospheres have been analyzed. The origin of the changes in optical absorption caused by the reducing/oxidizing treatments is discussed in terms of hydrogen and oxygen ion diffusion and the point defect structure of the material.