Inhibition effects of acetyl coumarines and thiazole derivatives on corrosion of zinc in acidic medium

The corrosion inhibition characteristics of acetyl coumarine (AC), bromo acetyl coumarine (BAC) and thiazole derivatives (BTMQ and BTCQ) on the corrosion of zinc in 0·1 M HCl solution were investigated by weight loss, potentiodynamic polarization and impedance techniques. The inhibition efficiency increased with increase in inhibitor concentration upto 5 ×10^− 4  M, then gave almost same inhibition efficiency. The polarization measurements indicated the mixed nature of inhibitors. The adsorption of compounds obeyed Langmuir’s adsorption isotherm. The thermodynamic functions for adsorption processes were evaluated.     

Local polarization reversal in LiNbO3 crystals

Local polarization reversal has been investigated in a thin surface layer of a ferroelectric and preliminary results are presented for lithium niobate. The polarization reversal is accomplished by using a moving pointed electrode. Pis’ma Zh. Tekh. Fiz. 23, 54–58 (June 12, 1997)     

Polarization switching time for semiconductor laser radiation

Expressions are derived for the polarization switching time for semiconductor laser radiation. These expressions can be used to assess the influence of the laser diode parameters on the polarization switching time of the output radiation. The results of an analysis of these expressions show that the main parameters influencing the polarization switching of the output radiation from a semiconductor laser are the nonlinear gains. Pis’ma Zh. Tekh. Fiz. 23, 87–95 (May 12, 1997)     

Polarization recording of holograms in partially polarized recording light

A theoretical approach is considered for media whose scalar and anisotropic responses are of opposite sign. The nondiffracted beam, and the imaginary and real images formed by a polarization hologram are analyzed under these conditions. It is shown that the imaginary image has its polarization transformed compared with the object field while a pseudoscopic object field reconstructed in terms of polarization state and degree is formed in the real image. Pis’ma Zh. Tekh. Fiz. 23, 38–42 (February 12, 1997)     

Modulational method of eliminating the zero shift of a fiber ring interferometer induced by polarization nonreciprocity

A new method is proposed to eliminate the zero shift of a fiber ring interferometer induced by polarization nonreciprocity. This method is based on periodic modulation of the polarization state of nonmonochromatic radiation at the entrance to the interferometer ring system. Numerical estimates are given. Pis’ma Zh. Tekh. Fiz. 25, 78–82 (August 26, 1999)     

Conversion of the polarization of an electromagnetic wave under cyclotron resonance in a two-dimensional electron system

A theoretical analysis is made of the conversion of the polarization of an electromagnetic wave when cyclotron resonance is excited in a two-dimensional electron system. It is shown that the greatest conversion of the polarization can be achieved in the reflected wave. At high electron concentrations the effect remains very appreciable even in the presence of electron scattering. In this case, the wave polarization conversion effect can be used to obtain information on electron relaxation in a two-dimensional system. Pis’ma Zh. Tekh. Fiz. 25, 21–26 (November 12, 1999)     

Local polarization reversal of LiNbO3 by scanning the surface perpendicular to the axis of spontaneous polarization with a needle-shaped electrode

The principle of local polarization reversal of ferroelectrics using a moving needle-shaped electrode¹ was used to make a comparative study of the characteristics of polarization reversal of LiNbO₃ from the Z(001) and Y(010) surfaces. In addition to chemical etching, an optical polarization method was used to visualize the domain structure. It was noted that the different dependences of the domain length on the polarizing voltage observed for the different crystal surfaces may be caused by the conducting and polarization properties of the regions in which the domain growth occurs. It is shown that the depth of penetration of the created domains in the sample may be set. Pis’ma Zh. Tekh. Fiz. 24, 52–57 (March 26, 1998)     

Polarization-induced curvature of a laser damage channel

Significant curvature of a laser damage channel in a metal has been observed and a correlation is reported between this effect and the polarization of the radiation. Pis’ma Zh. Tekh. Fiz. 23, 90–94 (May 26, 1997)     

Polarization switching with four-wave mixing of copropagating light waves in birefringent fibers

A system of equations is graphically solved that describes the copropagating interaction of four waves in a birefringent fiber. It is proposed to use this type of interaction for polarization switching. Pis’ma Zh. Tekh. Fiz. 23, 91–95 (November 12, 1997)     

Concerning the polarization vector of a wave reconstructed by a pseudodeep volume grating

It is shown theoretically and experimentally that for non-Bragg readout of a pseudodeep hologram recorded in a thick-layer medium the wave reconstructed by the hologram changes its state of polarization. Pis’ma Zh. Tekh. Fiz. 23, 58–63 (January 26, 1997)     

Faraday compensator of reciprocal optical anisotropy utilizing a polarization ring interferometer

It is shown that a polarization ring interferometer containing a Faraday cell can be used to compensate the reciprocal anisotropy in round-trip optical circuits. It is established theoretically and experimentally that, unlike the case of conventional Faraday mirrors, the quality of the restoration of the polarization in a compensator based on a polarization ring interferometer is practically independent of the Faraday rotation angle. A deviation of the Faraday rotation angle from 45° leads only to an additional power loss. The novel compensators can be used in fiber-optic circuits with a wideband light source or with several sources having different wavelengths. Pis’ma Zh. Tekh. Fiz. 25, 57–63 (May 26, 1999)     

Modulation of the polarization of semiconductor laser radiation at constant output power

The degree of polarization of “doubly”-modulated (by the pump current and the optical confinement factor) laser radiation is analyzed by applying a method of analyzing the stability of the solutions of systems of Lyapunov differential equations to a system of rate equations. An analysis of the system of rate equations yielded its eigenvalues, also called stability coefficients, which are the characteristic time for a transition of the system from one state to another. The behavior of a doubly modulated laser was modeled mathematically and it was demonstrated that the polarization of the laser output radiation can be controlled with almost constant output power. Pis’ma Zh. Tekh. Fiz. 24, 84–90 (August 26, 1998)     

Angular dependence of the signal in nonlinear polarization spectroscopy under conditions of noncollinear excitation by partially polarized radiation

The light-induced anisotropy tensor of initially isotropic media is calculated for the case of partially nominally polarized radiation. An analytic expression is obtained for the first time for the signal in a noncollinear nonlinear polarization spectroscopy system with a polarization-incoherent pump wave. Pis’ma Zh. Tekh. Fiz. 25, 79–82 (December 26, 1999)     

Dielectric properties of Be(IO<Subscript>3</Subscript>)<Subscript>2</Subscript>⋅4H<Subscript>2</Subscript>O crystals

The article studies the dielectric properties, dc conductivity and ac conductivity of Be(IO₃)₂⋅4H₂O single crystals. The dielectric constant ε has been defined for the three directions of the vectors a, b and c in the crystals in the temperature interval 280–340 K and frequency range 100 Hz–10⁶ Hz. The crystals show strongly expressed anisotropy, at 20 ^∘C and frequency 100 Hz ε_a = 235, ε_b = 30 and ε_c = 85. The frequency dependence of ε is evidence of the presence of low-frequency relaxation polarization in the crystals. The activation energies of the three directions in the crystals have been derived from the temperature dependence of dc conductivity, and they are 1.03 eV, 0.836 eV and 1.2 eV respectively.     

Electric dynamic fatigue in ferroelectric complex oxides

Data are presented on the fatigue of ferroelectric materials induced by cyclic polarization reversal by an ac field. It is suggested that the electric fatigue of the samples is caused by an increase in the defect concentration in the crystal structure. Pis’ma Zh. Tekh. Fiz. 24, 62–66 (April 26, 1998)     

Nonholonomic relation between the polarization state of light and the angle of twist of a single-mode optical fiber with linear birefringence

The relation between the polarization state of light in a twisted single-mode optical fiber possessing linear birefringence and the twist angle of the fiber is considered for the case of a fiber stretched in a straight line. It is shown that this reflection is of a nonholonomic character. Pis’ma Zh. Tekh. Fiz. 24, 22–25 (June 12, 1998)     

Superconducting-coil-resistor circuit with electric field quadratic in the current

It is shown for the first time that the observed [Phys. Lett. A 162, 105 (1992)] potential difference Θ_t between the resistor and the screen surrounding the circuit is caused by polarization of the resistor because of the kinetic energy of the electrons of the superconducting coil. The proportionality of Θ_t to the square of the current and to the length of the superconducting wire is explained. It is pointed out that measuring Θ _t makes it possible to determine the Fermi quasimomentum of the electrons of a metal resistor. Pis’ma Zh. Tekh. Fiz. 24, 7–11 (January 26, 1998)     

Characteristics of the excitation of ultrasonic waves by thin wafers of manganese zinc ferrite single crystals

It is suggested that thin wafers of a magnetostrictive material may be used as emitters of rf ultrasound. Single crystals of manganese zinc ferrite, which have high magnetostriction constants and low Foucault current losses, were used to investigate the orientational field dependences of the efficiency of excitation of acoustic waves having different polarizations. Some distinguishing features of the excitation of sound by single-crystal wafers compared with polycrystalline samples were observed, and the direction of propagation and polarization of the sound wave and its polarization relative to the crystallographic axes of manganese zinc ferrite with the highest conversion efficiency was identified. Pis’ma Zh. Tekh. Fiz. 24, 30–34 (March 26, 1998)     

Flexoelectric response of a liquid crystal layer with a temperature-induced orientational transition

It has been confirmed that the flexoelectric polarization model can provide an adequate interpretation of the temperature behavior of the electrical response of homeotropically oriented samples of n-methoxybenzylidene-n-butylaniline nematic liquid crystals at twice the excitation frequency. The temperature dependence of samples with different director orientations has been investigated experimentally. Pis’ma Zh. Tekh. Fiz. 23, 19–23 (May 12, 1997)     

Extension of a model analysis of the degree of polarization of light

A theoretical approach is developed in which partially polarized radiation can be represented as a sum of coherent and incoherent components and also of the action of some imaginary device with time-dependent birefringence. This approach allows the Jones vector matrix method to be used for the calculations, which is important for theoretical calculations of the polarization state. Pis’ma Zh. Tekh. Fiz. 25, 74–78 (April 12, 1999)