We suggest a method for optimizing geometry of acousto-optic (AO) interactions in anisotropic crystalline materials. Within the framework of this method, one gets global maximums of AO figure of merit M2 and their spatial orientations, proceeding from so-called “extreme” indicative surfaces, which are obtained after finding such an acoustic wave propagation direction that maximizes the M2 parameter for each propagation direction of the incident electromagnetic wave. The method improves earlier indicative surface-based techniques in several aspects, particularly in properly accounting for the momentum conservation condition for the AO diffraction, and yields a higher accuracy in assessing spatial anisotropy of the AO effect. We have constructed the extreme surfaces of LiNbO3 crystals for all possible cases, including those of isotropic/anisotropic AO diffractions and longitudinal/transverse acoustic waves. The anisotropy of the AO figure of merit for LiNbO3 is analyzed for the acoustic frequencies 0.01–2.0 GHz and the light wavelengths 405–1444 nm. The absolute M2 maximums refer to ‘indirect crystal cuts' and are equal to 26.3 × 10−15 s3/kg at 2 GHz and 405 nm, and 15.4 × 10−15 s3/kg at 0.4 GHz and 1444 nm.

Mach-Zehnder and conoscopic interferometry are used to explore photoelastic properties of anisotropic crystal materials. In a number of cases an application of both techniques significantly improves an accuracy of piezoop-tic and photoelastic measurements. The performance of such combined approach is demonstrated on tetragonal lithium tetraborate (LTB) single crystals, as an example. Special attention is paid to methodological and metrological aspects, such as measurement accuracy and the quantitative error analysis of the resulting measurements. Performing the interferometric measurements for different geometries of piezooptic coupling the full sets of piezooptic and photoelastic tensor constants of LTB crystals have been determined. The acoustooptic efficiency, on the other hand, has been evaluated using the magnitudes of photoelastic constants derived from the piezooptical measurements. For the geometries with strong photoelastic coupling LTB demonstrates quite large acous-tooptic performance with figure of merit value, М 2 , achieving 2.12 × 10 -15 s 3 /kg. It is several times larger than that of strontium borate crystals, nowadays the best acoustooptic material in deepultraviolet spectral region.

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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.

In this paper, the technology of growing ammonium dihydrogen phosphate (ADP) crystals in pores of nanoporous aluminum oxide (Al2O3) matrices was presented. On the grown nanocomposites, the optical properties of such structures were studied. In particular, the direct and diffuse optical transmission, as well as specular reflection of Al2O3 matrices with ADP crystals grown in nanopores, were analyzed. From the performed experimental studies, it can be concluded that the transmission and scattering of pure Al2O3 porous matrices and with ADP crystals in nanopores depends largely on the properties of the Al2O3 matrices and the technology of their production.