Quantum polarization and dielectric losses at low temperatures

We propose a mechanism for the quantum polarization of solid dielectrics, and use it to create and study the kinetic equation taking into account the tunneling of relaxation oscillators. The frequency dependences of both and tan are determined theoretically and compared with experiment. The density of thermally stimulated currents in the dielectrics are calculated. We find that one must take into account tunneling transitions of relaxation oscillators in order to explain the low-temperature features in the dielectric spectra.Translated from Izvestiya Vysshikh Uchebnykh Zavenenii, Fizika, No. 2, pp. 6–9, February, 1984.     

Investigation into the special features of the dielectric and polarization properties of lithiumtitanium ferrite ceramics

Loop-shaped dependences of the electric polarization on the electric field strength (the dielectric hysteresis) are registered for the first time for polycrystalline Li–Ti ferrite. Temperature evolution of the hysteresis loop parameters is investigated for ferrite samples. The results obtained can be interpreted from the viewpoint of the Maxwell–Wagner relaxation polarization or induced ferroelectric-like state in the electric ferrite subsystem.     

Analytical investigation into laser pulse heating and thermal stresses

Laser pulse heating of metallic surfaces results in rapid rise of temperature in the region irradiated by the laser beam. This in turn results in high temperature gradient in this region. The irradiated substrate material expands as a response to the temperature gradient. Consequently, high thermal stress levels are developed in the region of the high temperature gradient. In the present study, closed form solutions for temperature and stress fields due to a laser pulse decaying exponentially in time are presented. A Laplace transformation method is employed in the analysis. The resulting equations are non-dimensionalized with the appropriate parameters. It is found that temperature rises rapidly during the early heating period in the surface region. In this case, internal energy gain dominates the conduction losses from the surface vicinity. The thermal stress levels attain high values in the surface region. The stress wave developed is compressive and it propagates with a wave speed c₁ inside the substrate.     

Analytical approach to the impact of polarization aberration on lithographic imaging

An analytical approach to the impact of polarization aberration on lithographic imaging is proposed. The linear relationship between image placement error (IPE) of alternating phase-shifting mask (Alt-PSM) and odd aberration items of polarization aberrations, as well as that between best focus shift (BFS) of Alt-PSM and even aberration items of polarization aberrations are established by analytical equations, respectively. The validity of the linear relationships is demonstrated by numerical results. The differences and connections between scalar aberration and polarization aberration are briefly discussed based on these linear relationships.     

Phenomenological model of nonlinear dielectric losses related to the intrinsic conductivity of dielectrics

A phenomenological approach was applied to the dynamics of the intrinsic electric conductivity of dielectrics in an electric field in order to analyze its contribution to dielectric losses. The proposed differential equation contains only two parameters - the effective time of conductivity decay in an electric field, and , the time describing the recovery rate of the conductivity after switching off the field. The proposed approach predicts a linear dependence of specific conductivity of dielectrics on the sample thickness, as experimentally confirmed by Du Pont [1] for Teflon FEP. The field and time (or frequency) dependences of intrinsic conductivity and related dependences of dielectric losses were calculated, analyzed and illustrated with the published experimental data. The results show that the discussed contribution in dielectric losses is characterized by two hyperbolas (instead of one) while the distance between the branches depends on the intensity of applied electric field.Received: 3 November 2003, Published online: 29 June 2004PACS: 72.20.Ht High-field and nonlinear effects - 72.80.Sk Insulators - 77.22.Gm Dielectric loss and relaxation     

Theory of dielectric losses in ionic crystals

The orientation mechanism of associated structural point defects (dipoles, A- and K-dipoles) in an external electric field is considered. The kinetic equation for centrosymmetric crystals is obtained and solved. The buildup of polarization with time allows to investigate the temperature-dependence of the dielectric loss angle, and also the frequencies and defects of the structure. Comparison of the theory with available experimental data on alkali-halide crystal shows complete agreement.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 7–14, August, 1972.     

Spontaneous symmetry breaking due to polarization corrections

A model of self-interacting scalar and gravitational fields is constructed, in which the vacuum state with spontaneously broken symmetry arises as a solution of the field equations. The gravitational Lagrangian containing curvature-squared contributions is treated in the first-order formalism. The problems of cosmological singularities and conformal anomalies are discussed. In the case of vanishing Weyl tensor and constant scalar curvature, the curvature-squared contributions may be interpreted as being generated by the vacuum polarization, also in first-order formalism.     

Applications of the expanded basis method to study the properties of photonic crystals with frequency-dependent dielectric functions and dielectric losses

Band structures of two-dimensional photonic crystals (PCs) made of polar material with frequency-dependent dielectric constant are calculated by using an expanded basis method. The effect of the polariton gap (PG) of polar material on the photonic band gaps (PBGs) is explored. It is found that the PBGs are significantly modified near the PG, where the abrupt change of the dielectric constant appears. The feature of electromagnetic (EM) field is revealed when the frequency is located in the flat band. We display the equifrequency-surface configuration of the localized field and the spacial distributions of field. We observe the existence of several equi-ω curves for a specified frequency and the localized field distribution exhibiting various different patterns, dependent of the mode index. We also study the influence of the dielectric losses of the polar material on dispersion and find that the change of the real part of the Bloch wave vector is crucially related to the real part of the dielectric constant and the attenuated length is determined by its imaginary part.     

Fast-ion losses due to high-frequency MHD perturbations in the ASDEX upgrade Tokamak

Time-resolved energy and pitch angle measurements of fast-ion losses correlated in frequency and phase with high-frequency magnetohydrodynamic perturbations have been obtained for the first time in a magnetic fusion device and are presented here. A detailed analysis of fast-ion losses due to toroidal Alfvén eigenmodes has revealed the existence of a new core-localized magnetohydrodynamic perturbation, the sierpes mode. The sierpes mode is a non-Alfvénic instability which dominates the losses of fast ions in ion cyclotron resonance heated discharges, and it is named for its footprint in the spectrograms ("sierpes" means "snake" in Spanish). The sierpes mode has been reconstructed by means of highly resolved multichord soft-x-ray measurements.     

Ac dielectric losses and electrical conductivity of vanadium-borate glass

The conductivity and capacitance of bulk and thin-film metal-glass-metal structures with the glass based on the composition: 32.56% V₂O₅, 46.18% B₂O₃, and 21.26% CaO (mole %) are measured in the frequency interval 2·10²–2·10⁴ Hz and the temperature interval 300–500°K. The frequency-temperature dependences of the real and imaginary parts of the complex dielectric constant calculated from the results of the measurements indicate the presence of the process of relaxation polarization in the glass under investigation. The parameters of the relaxation process are determined. It is proposed that the presence of the relaxation component of the conductivity and losses is due to localization of small-radius polarons (SRP) in the vicinity of positively charged defect centers (bound SRP).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 85–89.     

Coupling losses in pigtailed optoelectronic modules due to fiber stresses

In pigtailed optoelectronic modules, a major source of optical coupling loss due to thermal or mechanical deformations of the assemblies is the stress exerted on the fiber in the package between its holding points. The stresses exerted on the fiber, the resulting strains on the holding points, and the risk of fiber fracture are examined using analytical models on the deformations undergone by the fiber. Optimization of fabrication assembly technology with regard to the risks of fiber fracture and optical coupling losses represents a tradeoff between these two risks.     

Radiation losses due to discontinuities in asymmetric three-layer optical waveguides

In this paper, the radiation losses caused by film thickness and refractive index discontinuities in asymmetric slab waveguides are examined theoretically. A technique developed by Mahmoud and Beal for dealing with the continuous part of the radiation spectrum is used. Several numerical examples which show the radiation loss for various waveguide configurations are presented and discussed and, where appropriate, comparisons with other related work made. In the case of asymmetric thickness steps, the radiation losses are found to be appreciably higher than those computed for symmetric guides. The radiation losses for guides having the same thickness were found to decrease as the guide thickness increased. Once the TE₁ mode become guided, the losses decreased rapidly. However, if the two guides had different thickness then it was found that the losses exhibited a minimum.     

Coupling losses in pigtailed optoelectronic modules due to fiber stresses

In pigtailed optoelectronic modules, a major source of optical coupling loss due to thermal or mechanical deformations of the assemblies is the stress exerted on the fiber in the package between its holding points. The stresses exerted on the fiber, the resulting strains on the holding points, and the risk of fiber fracture are examined using analytical models on the deformations undergone by the fiber. Optimization of fabrication assembly technology with regard to the risks of fiber fracture and optical coupling losses represents a tradeoff between these two risks.     

Analytical solutions to rate equations including losses describing threshold pumped fiber lasers

An exact analytical expression to the threshold pump power has been deduced for rate equations including loss coefficients applicable to fiber lasers doped with quasi two-energy-level ions. Following the derivation of a closed-form expression for the variation of the pump power along the fiber, together with analytical solutions to the position dependent atom population density and laser power in terms of the pump power, we have analytically and fully solved rate equations describing threshold pumped fiber lasers. A comparison has also been made between the exact analytical result with the previous reported results, which indicates that various approximation have underestimated the threshold pump powers.     

Microwave hall field inertia due to dielectric relaxation time

The magnetoresistive e.m.f. caused by microwave was measured as a function of _m in wide (3 cm – 4mm) range wave length. It has been found that Maxwell relaxation time does not influence the microwave Hall field lag in semiconductors. The discussion of these results is presented.