Zero shift in fiber ring interferometer with wideband radiation source

It is shown that the polarization zero shift of a fiber ring interferometer (FRI) is chiefly determined by the Stokes components of the radiation, which are circularly and linearly polarized at an angle of 45° to the axis of the polarizer. A birefringent element between the polarizer and coupler in conjunction with a wideband source results in disappearance of the FRI zero shift, regardless of the mutual orientations of the polarizer, coupler, and birefringent element.Moscow Physics and Technology Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 9, pp. 1001–1010, September, 1991.     

Increase in the correlation length of nonmonochromatic radiation during propagation in a single-mode optical fiber containing random inhomogeneities and the influence of this increase on the operation of a fiber ring interferometer

An analysis is made of the conditions under which the coupling of orthogonal polarization modes at random inhomogeneities in single-mode optical fibers leads to an increase in the correlation length of a source of nonmonochromatic radiation. It is shown that when long-base fiber ring interferometers with a single-mode fiber ring system possessing weak linear birefringence are used, the correlation length of the nonmonochromatic radiation at the interferometer exit is increased, which means that the interference pattern can have satisfactory visibility even when there is an appreciable difference between the interferometer arms as a result of the Sagnac effect due to the Earth’s rotation. The calculations were made by mathematical modeling of random inhomogeneities in the fiber. Zh. Tekh. Fiz. 69, 140–143 (July 1999)     

Analysis of nonlinearity in a high-resolution grating interferometer

Metrological feasibilities of a high-resolution grating interferometer (GI) based on a transverse Zeeman laser are investigated. When the grating pitch equals 20 μm, a resolution of 0.7 nm is obtained by means of a heterodyne signal processing method. The comparison of two approaches for determining the residual nonlinearity is presented. One is to evaluate the maximum residual error by determining the amplitude modulation degree of the measurement signal. The other is to do a high precision calibration with a differential dual-frequency interferometer that has a higher precision. The experimental results show that the nonlinearity is no more than 25 nm which fits well with the estimating result. Analysis of the depolarization effect of the grating indicates that it has little influence on the measurement accuracy.     

Dimensional characterization of opaque samples with a ring interferometer

In the present work, we introduce an optical method to characterize opaque samples. The technique combines low coherence interferometry with a ring configuration. This set-up, let us to obtain the thickness of the sample and the topography of both faces simultaneously by measuring the optical path difference with a reference arm. Experimental results in metal gauge blocks up to 1 mm are shown. A resolution better than 5 μm was obtained.     

A medium with optical activity depending on the incoherent light intensity in a ring interferometer: Models of processes

As part of the program of developing perspective incoherent optics systems in which synergy phenomena are realizable, a complex of models of processes in a nonlinear ring interferometer with an optically active medium whose rotary power depends on the incoherent radiation intensity in the nonlinear ring interferometer is constructed. The light intensity depends nonlinearly on the angle of polarization plane rotation. The analogy of the constructed models with the well-known model of the nonlinear ring interferometer with the Kerr medium and laser radiation is established. The (non)linearity of the models and the application of the corresponding nonlinear ring interferometers are discussed. The results obtained are important for improvement in methods of natural light field processing. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 26–34, June, 2007.     

Propagation of nonmonochromatic radiation in isotropic single-mode fibers with weak induced anisotropy

The change in the degree of polarization of nonmonochromatic radiation in isotropic single-mode fibers with a large h-parameter and small birefringence is examined.     

Switching behavior of a nonlinear Mach-Zehnder interferometer: Saturating nonlinearity

This paper uses the Beam Propagation Method to investigate numerically the switching behavior of a Nonlinear Mach-Zehnder Interferometer (NMZI). A saturating-type nonlinearity has been considered for the present investigations. It is shown that the input versus output characteristics change drastically when a Kerr type nonlinear medium is replaced by a saturating type nonlinear medium. In contrast to an NMZI with Kerr nonlinearity, where only quantitative behavior changes with NMZI length, quantitative as well as qualitative behaviors change in the case of a saturating nonlinearity. We propose an all-optical stabilizer and MZI with stable “ON” and “OFF” states on the basis of our investigation.     

Modeling a waveguide with a nonlinear insert with a quadratic nonlinearity

The scalar problem of the scattering of a wave from a nonlinear insertion lying in the interior of a waveguide is reduced by the incomplete Galerkin method to the boundary value problem for a Hamiltonian system. The cases in which this problem admits a solution in finite terms are indicated. Examples are given to illustrate specific phenomena due to the nonlinearity of the problem.     

Modeling of diffusion and absorption processes of tritium in beryllium membranes

The permeation of tritium produced in thermonuclear fusion through metallic membranes, which is a topical problem in radiation physics, is addressed. A physical model for the permeation of hydrogen through a beryllium membrane is proposed which takes into account the oxide layer on the surface of the membrane. The model is implemented in the form of a system of differential equations, which is solved by numerical methods. As a result of the computer modeling it is shown that as the temperature is raised, the oxide layer in a certain interval blocks the permeation of tritium in the membrane, and it is found that the tritium is distributed in a rather limited region of the membrane over its thickness. This circumstance will permit the use of special processing by etching or mechanical treatment. Zh. Tekh. Fiz. 69, 38–41 (July 1999) Deceased     

环形光源在干涉仪系统中的应用

 介绍了一种新的环形光源技术来抑制干涉仪系统的本征噪声以提高信噪比。阐述了环形光源抑制干涉仪系统本征噪声的原理,根据条纹对比度和需抑制噪声空间频率的要求,推导得到了环形光源的外半径和内半径。通过与传统的点光源对比实验表明：环形光源模式系统的本征噪声峰谷值小于点光源模式,且没有明显的牛顿环噪声,本征噪声的功率谱密度在空间频率小于2.5 mm ^-1时小于点光源的1/10,系统信噪比在空间频率小于2 ^-1时大于点光源的两倍。     

环形光源在干涉仪系统中的应用

介绍了一种新的环形光源技术来抑制干涉仪系统的本征噪声以提高信噪比。阐述了环形光源抑制干涉仪系统本征噪声的原理,根据条纹对比度和需抑制噪声空间频率的要求,推导得到了环形光源的外半径和内半径。通过与传统的点光源对比实验表明：环形光源模式系统的本征噪声峰谷值小于点光源模式,且没有明显的牛顿环噪声,本征噪声的功率谱密度在空间频率小于2.5 mm-1时小于点光源的1/10,系统信噪比在空间频率小于2 -1时大于点光源的两倍。     

Ultranarrow beams of electromagnetic radiation in media with a Kerr nonlinearity

The vector structure of a self-channeling electromagnetic field is determined by solving the complete system of Maxwell’s equations in a transparent medium with a Kerr nonlinearity. Self-channelling with an asymmetric angular distribution of the field occurs at powers several times the critical self-focusing power. As the power is increased, a universal (self-similar) field structure develops in which only the scales change as the power is varied. Self-channelling with a channel width much smaller than the (linear) wavelength of the light, i.e., a “needle of light” with an extreme concentration of radiant power, is found to occur. Zh. éksp. Teor. Fiz. 116, 458–468 (August 1999)     

Single-electron charging of triangular quantum dots in a ring interferometer

Small-size semiconductor ring interferometers operating in the Coulomb blockade regime have been experimentally and theoretically studied. The conductance as a function of the gate voltage exhibits narrow quasiperiodic peaks, which are further split into doublets. Based on the experimental structural data, a three-dimensional electrostatic potential, the energy spectrum, and the single-electron transport in the interferometer were modeled. The electron system can be divided into two triangular quantum dots connected by single-mode microcontacts to each other and to the reservoirs. A model of quantum dot charging in this system is proposed that explains the appearance of doublets in the conductance-gate voltage characteristics.     

Effect of orthogonal-mode random coupling on polarization characteristics of single-mode fiber lightguides (SMFL) and SMFL-based ring interferometers Part II. Zero drift in fiber ring interferometers with nonmonochromatic radiation sources

A method is proposed for calculation of the zero drift and Fedding interference signal at the output of a fiber ring interferometer (FRI) based on a single-mode fiber lightguide (SMFL) with a nonmonochromatic radiation source. The fiber length is divided into sections that are equal to the depolarization length in the SMFL. It is shown that when the FRI is made of an anisotropic SMFL with weak orthogonal-mode coupling, the calculation results agree with those obtained earlier by other calculation methods. Results for an FRI made of a weakly anisotropic SMFL with strong orthogonal-mode coupling are obtained for the first time.Institute of Applied Physics, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 11, pp. 1473–1480, November, 1994.     

The use of the diffusion approximation for simulating radiation and thermal processes in the skin

Radiation and thermal processes in skin exposed to solar radiation are simulated based on the diffusion model of radiative-conductive heat exchange. Using the model proposed for the parameters corresponding to radiation with a wavelength of 800 nm, the contributions of thermal radiation induced by the skin and the reflection and refraction effects are estimated, and the photoprotective properties of titanium dioxide nanoparticles (TiO₂) when introduced into the stratum corneum are studied.