Том 124, № 3 (2018)

The possibility is demonstrated of a precision frequency measurement for the 1¹S₀−2³S₁ forbidden transition (at 62.6 nm) of a helium atom using the stimulated Raman scattering method. The 1¹S₀ singlet state is the ground state of ⁴He, while the metastable 2³S₁ state has the lowest energy in the triplet part of the spectrum (⁴He*). The transition has a very small natural width, which allows us to consider it as a possible reference for creation of a frequency standard in the vacuum ultraviolet region.

A technique is proposed for determining the pore-size distribution based on measuring the dependence of total reflectance in the domain of partial transparency of a material. An assumption about equality of scattering-coefficient spectra determined by solving the inverse radiation transfer problem and by theoretical calculation with the Mie theory is used. The technique is applied to studying a quartz ceramics. The poresize distribution is also determined using mercury and gas porosimetry. All three methods are shown to produce close results for pores with diameters of <180 nm, which occupy ~90% of the void volume. In the domain of pore dimensions of >180 nm, the methods show differences that might be related to both specific procedural features and the structural properties of ceramics. The spectral-scattering method has a number of advantages over traditional porosimetry, and it can be viewed as a routine industrial technique.

Spectral optical constants of pyrolytic carbon in the region of activity of the E_1u vibrational mode are calculated within the framework of the effective-medium approach in the Bruggeman approximation. It is demonstrated that the number, position, half-width, and relative intensity of the selective-absorption bands in the IR absorption spectrum of pyrolytic carbon are the independent of porosity of the original absorbing object.

Specific features of the energy-band structure of magneto-photonic crystals have been studied. The problem of the propagation of light through a finite layer of a magneto-photonic crystal has been solved by the modified Ambartsumyan layer-summation method. The effect of the direction of an external magnetic field on the band structure has been studied in detail and shown to alter the number of forbidden bands, change the frequency widths of these bands, and modify their polarization-related properties. Such systems have been shown to possess four eigenpolarizations.

The formation dynamics of oxide nanostructures on surfaces of oxidized aluminum and beryllium with water at room temperature and under radiation action has been studied by the radiothermoluminescence method. The role of intermediate surface active particles in the dynamics of changes of the oxidation process of aluminum and beryllium in an absorbed dose range of 0.5–120 kGy has been considered. It is established that, when nanostructure films are formed, molecular oxygen and other oxygen-containing ion-radical groups generated by γ irradiation play the main role. The radiation-oxidation kinetics of aluminum and beryllium is studied, and their chemisorption passivation is revealed. A possible mechanism of this process is discussed.

Since last few decades optics has already proved its strong potentiality for conducting parallel logic, arithmetic and algebraic operations due to its super-fast speed in communication and computation. So many different logical and sequential operations using all optical frequency encoding technique have been proposed by several authors. Here, we have keened out all optical dibit representation technique, which has the advantages of high speed operation as well as reducing the bit error problem. Exploiting this phenomenon, we have proposed all optical frequency encoded dibit based XOR and XNOR logic gates using the optical switches like add/drop multiplexer (ADM) and reflected semiconductor optical amplifier (RSOA). Also the operations of these gates have been verified through proper simulation using MATLAB (R2008a).

We consider the sizes of a region in a three-dimensional space in which an optical wave field excites mutually coherent perturbations. We discuss the conditions under which the length of this region along the direction of propagation of the wave field and, correspondingly, its volume are determined either by the width of the frequency spectrum of the field or by the width of its angular spectrum, or by the parameters of these spectra simultaneously. We obtain expressions for estimating extremely small values of the coherence volume of the fields with a broad frequency spectrum and an extremely broad angular spectrum. Using the notion of instantaneous speckle-modulation of the wave field, we give a physical interpretation to the occurrence of a limited coherence volume of the field. The length of the spatiotemporal coherence region in which mutually coherent perturbations occur at different times is determined. The coherence volume of a wave field that illuminates an object in high-resolution microscopy with frequency broadband light is considered. The conditions for the dominant influence of the angular or frequency spectra on the longitudinal length of the coherence region are given, and the conditions for the influence of the frequency spectrum width on the transverse coherence of the wave field are examined. We show that, when using fields with broad and ultrabroad spectra in high-resolution microscopy, this influence should be taken into account.

The results of studies that have been performed over the last decade in the field of development of silver halide and nonsilver holographic recording media of organic and inorganic origin are analyzed. It is shown that previously developed materials mainly allow the development of holographic investigations. Among irreversible materials, considerable progress has been made in improving the characteristics of photopolymerizable recording media, which has allowed their use in color image holography and 3D optical archive-type memory, as well as for fabricating holographic optical elements. In the field of improving the properties of reversible holographic recording media, practically significant results have been obtained for the creation of photoanisotropic materials based on azo dyes experiencing cis–trans photoisomerization, which allow the recording of polarization holograms. The needs of dynamic holography have been satisfied by lightsensitive doped inorganic crystals and polymer layers that have been created with nonlinear optical properties.

Results of studying optoacoustic characteristics of pentaerythritol tetranitrate (PETN) specimens with inclusions of ultrafine aluminum particles (100 nm) are presented. Regularities of the increase of extinction coefficient k_ef and signal amplitude U on a piezodetector by increasing laser-pulse fluence H have been established. Estimates have been made, and it has been concluded that, during a laser pulse, heating of aluminum inclusions and a shell surrounding it occurs up to a gasification temperature and appear craters on a specimen’s surface appear at H > 0.1 J/cm².

The linear thermal-expansion coefficient of polymethacrylate is measured in the temperature range from–194 to 0°С. A dilatometric study was performed using optical diffraction.

We have designed and fabricated four LDA optical setups consisting of aberration compensated four different compact two hololens imaging systems. We have experimentally investigated and realized a hololens recording geometry which is interferogram of converging spherical wavefront with mutually coherent planar wavefront. Proposed real time monitoring and actual fringe field analysis techniques allow complete characterizations of fringes formed at measurement volume and permit to evaluate beam quality, alignment and fringe uniformity with greater precision. After experimentally analyzing the fringes formed at measurement volume by all four imaging systems, it is found that fringes obtained using compact two hololens imaging systems get improved both qualitatively and quantitatively compared to that obtained using conventional imaging system. Results indicate qualitative improvement of non-uniformity in fringe thickness and micro intensity variations perpendicular to the fringes, and quantitative improvement of 39.25% in overall average normalized standard deviations of fringe width formed by compact two hololens imaging systems compare to that of conventional imaging system.

Equation (25) should be read as follows: