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During the Coronavirus infection pandemic (20192021), the admission of patients from antituberculosis dispensaries decreased (2261 vs 2747 in 20162018). At the same time, the number of patients with tuberculous haematogenous uveitides decreased significantly (55% vs 76%; р 0.0001), and that with non-tuberculous ophthalmic diseases by contrast significantly increased (23% vs 43%; р 0.0001). Among tuberculous uveitides, high amount of chorioretinitis (46%) and of panuveitis (11%) was found. Their severity was escalated by complications (in 7786% of patients) and frequent concomitant systemic conditions. In 277 patients, the post-covid syndrome was revealed (after prior Coronavirus COVID-19 infection). During the pandemic, the admission to the sanatorium of patients with active (dispensary follow-up care group I) and chronic (dispensary follow-up care group II) forms of ocular tuberculosis significantly decreased: 9% vs 15%, and 18% vs 27%, respectively; that with clinical recovery (dispensary follow-up care group III) increased (73% vs 58%). Active tuberculosis forms of other localization were excluded. A reduction in the quality of ocular tuberculosis diagnosis and treatment in dispensaries is related to decrease in number of qualified phtisioophthalmologists, periodical breakdowns in supply of tuberculin and of some medications. In the Krasny Val sanatorium, patients received additional examination, full-fledged chemotherapy, and necessary rehabilitation.

One of the most important educational goals of modern school is to prepare students for the successful completion of final exams. The structure of the Unified Sate Exam in profile-level mathematics includes the proof of increased complexity for geometric problems, requiring students to have a comprehensive knowledge of planimetry. The most important feature is the lack of unified algorithms for solving such problems; the success largely depends on the students’ experience in solving combined planimetric problems. Nevertheless, the practice of solution allowed us to identify some geometric structures that are auxiliary keys to finding the right solution. One of these keys was the auxiliary circle method, which is presented in this paper. The paper describes the essence of the method and the conditions of its application, examines the proofs for the problems taken from real test and measurement materials of the exam, and considers the solutions of the problems in the framework of the described method.

We calculate the amplitudes of surface plasmon-polaritons (SPP) excited at a photonic-crystal–metal interface. Using a three-wave approximation, we evaluate optical fields in the crystal medium. The generation of plasmons at the boundary between the photonic crystal (PhC) and gold substrate is numerically analyzed in the wavelength range of a plane incident wave 400–1,900 nm. The optimum wavelength corresponding to the maximum plasmon amplitude is determined.

The development of diagnostic and therapeutic capabilities in hematology contributed to a growth in survival rate in patients with acute leukemia and to the increase in number of different ocular conditions as rare signs of hemoblastosis recurrence and treatments side effects. We observed a female patient with extramedullar leukemic ocular damage in acute lymphoblastic leukemia. It is noteworthy that the process of ocular involvement into the underlying disease occurred on the background of complete confirmed hematologic remission.

We present the coupled-mode equations for inclined waves in photonic crystals. Among the eigenmodes, we focus on the evanescent modes. We consider the conjugation of the waves at the interface of the crystal and its metallic substrate. We underscore the role of resonant coupling of the fields at this interface and briefly discuss the field structure in the open space.

Optical fields are studied in a planar channel inside a metal layer taking into account a complex dielectric function of the metal. An influence of an exit aperture on the incident field propagating along the channel is considered; a mathematical approach is developed for analysing the effect. Attention is paid to the fact that the incident field should not be assumed a priori known if the wave transformation at the exit is neglected. For a chosen dimension of the channel and parameters of a metal, the coefficients for the lowest mode transformation into higher modes are found. The spatial field structure at the exit aperture and on the exit surface of a metal is studied. Existence of domains possessing an anomalously high intensity is revealed.

The transmission of an evanescent light wave through the subwavelength aperture of a dielectric cylindrical metal-coated waveguide is studied. The theoretical approach to the description of the field structure in such a nanowaveguide is developed, which takes into account the transformation of the initial wave reflected from the output aperture and proves applicable when dielectric properties of a real metal are taken into account. The complex reflection coefficient of a supercritical waveguide mode from the aperture, the complex light flow and the far-field transmission coefficient are calculated for an aluminium-coated waveguide at the light wavelength of λ = 488 nm. It is established that the reflection and transmission coefficients of the nanowaveguide strongly depend on the dielectric constant of its core and differ significantly for transverse-magnetic and transverse-electric modes. It is demonstrated that the characteristics of light fields under study differ essentially from those of a nanowaveguide with ideally conducting walls and the subwavelength aperture in a perfectly conducting screen.

The transmission of an evanescence electromagnetic wave through the subwavelength aperture of a dielectric cylindrical metal-coated waveguide is studied. In the ideal metal approximation a theoretical approach to the description of the field structure in a nanowaveguide is developed, which takes into account the transformation of the initial wave reflected from the output aperture. The complex reflection coefficient of a supercritical waveguide mode from the subwavelength aperture is calculated. The dependence of the field structure at the waveguide output on the ratio of its radius to the optical wavelength and on the dielectric constants of the waveguide core and the environment is found. The conditions for the appearance of a plasmon resonance in the presence of a medium with the negative dielectric constant in front of the input hole of the waveguide are found.

The results of theoretical considerations of the electromagnetic-field behavior in a truncated cylindrical waveguide with a subwavelength-sized exit hole are reported. We develop a self-consistent approach to the description of the transverse-magnetic (TM) and transverse-electric (TE) fields inside the waveguide and in the free space behind the exit aperture of the waveguide. The approach takes into account the transformation of the initial wave into all possible modes that appear upon reflection from the exit aperture of the waveguide. It allows us to evaluate the amplitude reflection coefficients for the evanescent TM and TE waves and express them in terms of the impedance of an infinite waveguide and the impedance of the exit aperture at the interface of the truncated waveguide and the free space. We determine the complex optical flow through a nanometric hole and the transmission coefficient to the far-field zone and express them through the reflection coefficient. It is shown that the reflection and transmission coefficients strongly depend on the ratio of the aperture radius to the light wavelength, the dielectric constants of the waveguide core and the surrounding matter, and the type of waveguide modes. It is demonstrated that, in the case of a metallic matter at the waveguide exit, there is a strong enhancement in the amplitude of the reflected wave and, hence, in the resulting amplitude of the tangential component of the electric field. This enhancement is a result of the plasmon-supported effects in a metallic substrate.

The theory of light transmission through the aperture-type near-field optical probe with a semiconducting matter in its core is presented. It is based on the exact description of the transverse-magnetic (TM) and transverse-electric (TE) eigenmodes inside a conical waveguide with perfectly conducting metallic walls and a dissipative core described by a complex frequency-dependent dielectric function. We concentrate on evaluating the energy density distribution of the electromagnetic field inside a probe with a subwavelength aperture including the region near the tip exit, where it is mainly determined by the contribution of evanescent waves. Significant attention is paid to detailed calculations of the near-field transmission coefficient for semiconducting (GaP, GaN, GaAs, and Si) probes of mesoscopic length and to a comparison of the results obtained with those for the dielectric (SiO2, Si3N4, and diamond) probes. Our calculations indicate a strong enhancement in the transmission efficiency of the semiconducting near-field probes with a high refractive index both in the visible and near-infrared spectral ranges as compared to the conventional fiber or solid quartz tips. It is shown that the optical transmittance for the dominant transverse-electric (TE11) mode is significantly greater than that for the lowest-order transverse-magnetic (TM01) mode.

A solution to the phase problem in optics is considered within the context of the analysis of signals changing in time and of the effect of an object under investigation on the probing radiation. The solution is based on the use of a twin-wave interferometer with phase modulation in one of the channels and a spectrometer. The analysis is concerned, in particular, with signals and processes of ultrashort duration. To shift the frequency in the interferometer channel, an electrooptical crystal of ferroelectric perovskite is used as the modulator. Errors of amplitude and phase structures determined are analyzed.

The spatial distribution of monochromatic light fields is studied in a tapered silicon fibre with the subwavelength aperture. The lowest-order electric TM01 mode is analysed theoretically in a cone with perfectly reflecting metal walls filled with a light absorbing medium. Exact formulas and approximate expressions are obtained for a medium with the complex permittivity, which describe the spatial dependences of the electric and magnetic energy densities inside the cone. The behaviour of the field at the waveguide exit is analysed for the aperture diameter as small as ~1/30 of the wavelength. The main attention is devoted to the transmission coefficients of the probe, which were calculated for a wide range of its geometrical parameters in the wavelength region from 400 to 830 nm. It is found that silicon provides a substantial increase in the output light energy density at the optical probe end both in the IR and visible spectral regions compared to glass.

The spatial structure of light waves of the electric type in a cone with perfectly reflecting metal walls is theoretically analysed. The exact formulas and asymptotic expressions are derived which describe the dependences of the energy density of different components of the field inside the cone on the radial coordinate. A special attention is paid to the study of the character of the field decrease near the cone apex depending on the cone angle and the wavelength. The effects of reflection of waves from the truncated cone-free space interface are studied. The obtained results are used for measuring the transmission coefficient of a truncated cone in the optical range for a broad range of parameters, including the diameter of the output aperture of the order of 0.05 — 0.1 of the wavelength. The possibility of obtaining a high transmission coefficient of light in a truncated metallised cone is theoretically substantiated.

The spatial structure of light waves of the electric type in a cone with perfectly reflecting metal walls is studied. Exact formulas defining dependences of energy densities of various field components inside the cone on the radial coordinate and polar angle are presented. Simple asymptotic expressions for the field components are derived. They are applicable when the distances from the cone vertex significantly exceed the wavelength of the light wave. The behavior of the field near the vertex as a function of its taper angle and the wavelength of the light wave for the fundamental electric-type mode is studied in detail. A theoretical approach for the quantitative description of wave reflection at the interface of the truncated cone and free space is proposed. The reflection effects of light waves in a truncated cone at the exit aperture of the subwavelength cross section are calculated on the basis of this approach. Particular attention has been concentrated on calculations and analysis of the dependences of the transmission coefficient of the truncated cone on the wavelength and geometric parameters of the system. The results obtained cover the spectral region from 400 nm up to 1000 nm and a wide range of cone taper angles and exit aperture diameters up to about 1/20 of the wavelength. The possibility of obtaining a high coefficient of light transmission in a metallized truncated cone is theoretically demonstrated.

The penetration of an H wave through a waveguide whose radius varies continuously from about the wavelength size to subwavelength dimensions (of the order of 1/10 wavelength) is calculated. The method for the field analysis is developed and the range of its applicability is studied by considering some numerical examples. The dependence of the transmission coefficient of a tapered waveguide on the radiation wavelength and on the profile steepness of the waveguide is studied. It is shown that a sharper decrease in the waveguide radius provides higher values of the field transmission coefficients.

The characteristics of electromagnetic waves in a narrowing waveguide are investigated. A method for field analysis is developed based on the application of transverse modes parametrically dependent on the longitudinal coordinate. For a circular cross section waveguide, a system of equations for the wave amplitudes is obtained, the waves being coupled owing to a variable tilt of the walls. It is shown that in the adiabatic approximation, there exist independent eigenwaves whose structure reflects the field energy density variation due to the waveguide radius variation. A detailed analytical and numerical investigation of these fields has been carried out for a waveguide with a special profile of “hypergeometric” type. The applicability of the adiabatic approximation is studied and conversion of the fundamental mode into higher-order modes is assessed. The amplitudes of the higher-order modes are obtained using the Green function for ordinary differential equations. The region of the waveguide parameters is found where the higher-order mode amplitudes are not great and the adiabatic approximation is highly accurate. The dependence of the transmittance of a semi-infinite waveguide on the input radiation characteristics is obtained. It is established that the field amplitudes at the waveguide output strongly depend on the wavelength of the input radiation, on its transverse structure, and the waveguide profile steepness. The greatest output fields take place in the case of an abrupt dependence of the waveguide radius on the longitudinal coordinate.

A uniform cylindrical waveguide containing an amplifying medium is shown to have no frequency cutoff. There, waves of an arbitrary frequency increase in the direction of propagation, and the increment obtained for small waveguide cross sections is inversely proportional to the waveguide diameter. A nonuniform waveguide consisting of amplifying and absorption sections is also analysed. The transmittance of this waveguide for below-cutoff waves is considerably higher than the transmittance of a uniform passive waveguide.

An approximate pattern of calculation of the field behavior in waveguides of variable radius is proposed. It is based on the assumption of a slow dependence of the radius on the longitudinal coordinate and is reduced to the solution of an ordinary differential equation. The dependences of the waveguide transmission on the frequency of radiation, entrance and exit radii, as well as the rate of radius variation along the axis are studied. The analysis is carried out within the range of parameters typical for optical fibers used in optical near‐field microscopy. It is shown that the increase in the rate of radius variation with the longitudinal coordinate will cause the transmission coefficient of the tapered waveguide to increase.

A mathematical method of reconstruction of a function from its Gabor transform is described. The reconstruction requires data only on the modulus of the Gabor expansion. An analysis is made of transformations of light signals that are produced in some optical systems including the spectral expansion. It is shown that the combination of these systems with appropriate mathematical processing is able to provide a very high time resolution in the analysis of arbitrary signals.

A novel approach is proposed for reconstruction of the temporal characteristics of radiation from the results of nonlinear—optical measurements. A description is given of an algorithm for the processing of a two-dimensional set of data, based on inversion of the Gabor transform. This algorithm makes it possible to reconstruct arbitrary temporal signals, including multipulse signals, in the absence of any a priori information on their profile.

A new method is proposed for the measurement of the characteristics of short optical signals. This method is based on spectral expansion combined with temporal scanning by a streak camera, and on a special mathematical algorithm for reconstruction of the initial signal. The capabilities of the method are illustrated with examples obtained by computer simulation. An estimate is obtained of the dependence of the results of such reconstruction on the noise present in the measured data. It is shown that the temporal resolution of the method can be one or two orders of magnitude higher than the intrinsic resolution of electron-optical apparatus.

A study is reported of the characteristics of the principal wave in an optical coaxial metal waveguide. The real properties of metals at optical frequencies are taken into account. An approximate formula is derived for the dependences of the eigenvalues of the transverse wave vectors on the geometric parameters of a coaxial line and on its permittivity. The exact eigenvalues are determined for several values of the parameters of practical interest. It is shown that such a coaxial line can concentrate radiation with domains much smaller than the radiation wavelength.

An analysis is made of a method for determining the time characteristics of radiation. This method is capable of recording the fine temporal structure that cannot be detected on the basis of the intrinsic temporal resolution of the recording apparatus. An estimate is given of the precision of the method which depends on the parameters of the method and on the accuracy of measurement of the quantities.

The characteristics of optical waves in amplifying dielectric periodic nanostructures are studied. The formula for the dependence of the wave number on frequency, which comprises a photonic band gap and is valid for structures possessing a complex dielectric function, is obtained. It is shown that the gain is anomalously high at frequencies residing in the photonic band gap.

The findings from studies on structural and functional parameters of the adrenal, thyroid, and pineal glands in conditions of ovarian hypofunction and after its correction by laser puncture are presented. An experimentally induced hypofunction of the ovaries was shown to be accompanied by a decreased hormonal synthesis in the cortical fascicular zone. The epiphysis showed ultra structural signs of increased functional activity. Application of a helium-neon laser to biologically active points of the ovarian reflexogenic zone induced normalization of the ovarian cycle, potentiating of the adrenal functional state, and a decreased thyroid hormone production and abolished the activatory effect of the dark regime on the functional state of the pineal gland.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Propagation of the wave of Stimulated Raman Scattering (SRS) in waveguide is studied, on conditions that it is filled with some Raman-active material and that a pump wave is present inside. The features of the SRS-wave are analyzed, assuming the wave frequency to be close to the critical value.

An expression is obtained for the reconstruction of a complex optical signal from the modulus of the Gabor transform of the signal spectrum. It is shown that the temporal resolution of systems with an image-converter streak camera can be improved by spectral expansion of the signal and by mathematical processing of the results obtained.

A new method is proposed for an analysis of amplitude?phase characteristics of short laser radiation pulses. The method is based on determination of a pattern of the interference between the spectra of the investigated pulse and of a second pulse obtained from the original one by a frequency shift. An analysis of the intensity distribution in the spectral interference pattern can yield the phases of the spectral components, which?in combination with the conventional spectrum?provides complete information on the time dependence of the signal.

A new technique is proposed for the characterization of ultrashort optical pulses. The technique includes a simple mathematical treatment of the time-resolved spectrum of the signal that is obtained using an image converter camera. The theoretical description of the technique and several numerical examples modeling the ultrashort pulse reconstruction are presented. The dependence of the reconstruction result on the noise level is evaluated. It is shown that the temporal resolution of the technique can be up to two orders of magnitude higher than that for the used electro-optic device.

A study is made of the characteristics of wavefront reversal in a resonantly amplifying medium. The region of the effective interaction between waves is of finite size and the phase relationships between the constant and alternating components of the resultant signal influence the signal increment.

A study is made of the propagation of a light wave having a complex transverse structure in an amplifier under saturation conditions. An equation is obtained for the signal-to-noise ratio at the amplifier exit.

Studies on the retrieval of a complex function from data on its modulus and the modulus of its Fourier spectrum are briefly reviewed. An analog optical method of solving this same problem is described. Pictorial explanations are presented concerning the ambiguity of the retrieval of a spectrally bounded one-dimensional function from a single modulus. Some methods of retrieval of time characteristics of radiation are analyzed from the standpoint of the phase retrieval problem that rests on spectral measurements or on measurements of the autocorrelation function.

A theoretical investigation is made of conversion (in an amplifier) of the image of a signal consisting of a wave with a pseudorandom transverse structure and a plane wave. Equations are obtained for the description of the mutual influence of these waves under saturation conditions. The results of calculations demonstrate a considerable change in the ratio of the intensities of these waves as a result of amplification.

A theoretical analysis is given of the interaction between laser radiation and a bleachable filter in the presence of mismatch between the working frequency of the filter and the frequency of the laser radiation. It is shown that considerable phase modulation of the radiation may occur as a result of the increase in the transparency of the filter. Estimates are given of the contributions of the amplitude and phase modulation to the width of the spectrum.

A theory of the development of mode locking in a ring laser is given. Equations are obtained for the relationship between, the forward and reverse waves in the course of bleaching of a nonlinear filter. The equations are compared with the time characteristics of the forward and reverse waves in a ring laser determined experimentally with an image-converter camera. It is shown that the time characteristics of the forward and reverse waves are strongly correlated when the concentration of the bleachable absorber is high, but this correlation becomes weaker with decreasing concentration of the absorber.

A review is given of the theory of the generation of ultrashort light pulses in lasers with bleachable filters. Attention is mainly concentrated on the statistical aspects of the formation of ultrashort light pulses in such lasers. The topics discussed include the formation of laser modes, the narrowing of the spectrum in the stage before the bleaching of the filter, the transformation of the field profile during the bleaching process, the statistics of the appearance of single ultrashort pulses, and the influence of the gain saturation on the time characteristics of the radiation. Several additional effects, which influence the final structure of the radiation, are considered. A quantitative theory is given of the widely used two-photon method for measuring ultrashort pulses and a basic shortcoming of this method is pointed out: it is not possible to find whether one or many pulses appear in a given period.

An optical scheme is proposed for the reconstruction of the phase distribution of the light field from two amplitude distributions. A mathematical algorithm is developed, which models the operation of the scheme. Numerical calculations revealed the rapid convergence of the algorithm.

An analysis is made of a photoelectric recording method based on the use of an unsteady reference wave. The object field is recorded after a preliminary conversion into a spatial spectrum, which is performed by an optical method. The signal can be recorded on magnetic tape, transmitted along communication channels, and reproduced as a transparency on the screen of an image converter. The field reconstructed from such a transparency is identical with the original object field. The proposed method makes it possible to reduce the amount of the information that has to be recorded. The object field can be recorded directly in difficult spectral regions. The inverse Fourier transformation is performed during the reconstruction in the visible part of the spectrum.

A description is given of a proposed system for continuous recording and reproduction of a holographic cine film. The system is based on the use of a uniformly moving photographic film and a reference wave formed by a diffuser.

A theoretical study is made of the resonant amplification of two plane waves propagating at a small angle relative to one another. A system of equations describing the interaction between the waves in the case of saturation of the resonant transition is derived and solved analytically. The difference between the ratios of the wave intensities at the input and ouput of such an amplifier is discussed.

An expression is obtained for the Wigner function of a paraxial light beam in terms of its intensity distribution in a bulk (three-dimensional) medium. The derivation is given for monochromatic beams with a one-dimensional transverse structure and it is based on application of the Radon transformation.

An optical system is proposed for the reconstruction of an amplitude-phase distribution of an optical field from two amplitude functions recorded in different planes.

It is shown that interaction between an optical signal and a special nonmonochromatic reference wave with a bulk light-sensitive material can be used to record information on the spatial and temporal characteristics of the signal. Illumination of a hologram obtained in this way with a special reconstructing wave produces a three-dimensional time-dependent image of the original object. The amount of information which can be recorded in this way is calculated.

An analysis is made of diffraction-caused distortions of a special reference wave needed in continuous holographic recording of transient optical fields. It is shown that telescopic systems should be used in order to image the reference wave in the required region in space. Phase distortions appear unavoidably if nontelescopic systems are used. Features of the formation of a reference wave in a two-prism electrooptic cell are considered under quasistatic conditions. It is shown that in this case phase distortions may be compensated by a cylindrical lens.