Determination of the crack configuration in an anisotropic elastic medium

The problem of the identification of a single internal crack in an anisotropic elastic body is investigated. Using the dislocation theory approach, a system of boundary integral equations for the crack opening functions is constructed and studied by the boundary element method. A crack identification method is developed on the basis of the crack parametrization by a finite number of parameters, with their subsequent determination through the minimization of a certain nonquadratic residual functional. The problem of identifying a transverse tunnel crack in an orthotropic layer is solved for the cases of plane and antiplane deformations.     

Optical Tamm mode based refractometer in all-dielectric configuration

Optical Tamm (OT) modes formed at the interface of distributed-Bragg reflector (DBR) and low-index dielectric material, exhibit strong dispersive features at optical frequencies which gives rise to the possibility of designing refractometer with improved sensitivity. Using this idea, we design a TiO₂/SiO₂ based DBR configuration for sensing refractive-index changes around 1.33 using spectral-interrogation as well as angular-interrogation method. Dispersion characteristics of OT modes in the DBR configuration are tailored to obtain spectral sensitivity ∼1200 nm/RIU and angular sensitivity ∼40°/RIU for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. We also show that the sensitivity could be substantially tuned over a wide range by appropriately choosing the thicknesses of DBR constituent layer. An all-dielectric DBR configuration gives rise to the possibility of realizing refractometer in any desired spectral region by linearly translating the dispersive behavior of photonic bandgap (PBG) guided OT modes.     

Adiabatic propagation of quantized light pulses in an atomic medium with the tripod level configuration

We consider adiabatic propagation of a pair of quantized light pulses in a coherently prepared atomic medium with the tripod level configuration. We find that under conditions of electromagnetically induced transparency, two distinct polariton modes are simultaneously formed in the medium. These polaritons, represented by certain coherent superpositions of the quantized fields, have different group velocities; the fast one propagates at essentially the speed of light, while the group velocity of the slow polariton can be dynamically reduced to zero. The state mapping between the electromagnetic field and atomic ensemble is also demonstrated. The text was submitted by the author in English.     

Normal mode splitting in hybrid BEC-optomechanical system

We consider an opto-mechanical cavity system consisting of Bose-Einstein condensate (BEC), trapped inside the optical cavity and driven by single mode laser field. The intracavity field acts as nonlinear spring which couples the condensate mode with moving end mirror of the cavity. We study the occurrence of normal mode splitting in the position spectra of the mechanical oscillator and condensate mode as a consequence of hybridization of the fluctuations of intracavity field, mechanical mode and condensate mode. We also discuss the modification in the dynamics of the mechanical oscillator due to frequency of the collective oscillations of cold atoms and the back action of the atoms on the mechanical mirror. Moreover, we investigate the normal mode splitting in the transmission spectrum of cavity field.     

The surface mode supported by an asymmetrical waveguide containing left-handed materials

The propagating characteristics of surface mode supported by an asymmetrical three-layer waveguide containing left-hand materials are studied in detail. The forward and the backward surface modes have been identified respectively through the slope of dispersion curve and the total energy flux of the structure. Research shows that anti-symmetry mode corresponds to forward surface wave. Furthermore, to symmetry mode, the type of surface mode depends on the distribution of the electric field in the left-handed layer. It is found that, the conversion between backward surface wave and forward surface wave is realizable by varying the thickness of the left-handed layer and the permittivity of the substrate.     

Normal mode splitting and mechanical effects of an optical lattice in a ring cavity

A novel regime of atom-cavity physics is explored, arising when large atom samples dispersively interact with high-finesse optical cavities. A stable far-detuned optical lattice of several million rubidium atoms is formed inside an optical ring resonator by coupling equal amounts of laser light to each propagation direction of a longitudinal cavity mode. An adjacent longitudinal mode, detuned by about 3 GHz, is used to perform probe transmission spectroscopy of the system. The atom-cavity coupling for the lattice beams and the probe is dispersive and dissipation results only from the finite photon-storage time. The observation of two well-resolved normal modes demonstrates the regime of strong cooperative coupling. The details of the normal mode spectrum reveal mechanical effects associated with the retroaction of the probe upon the optical lattice.     

Electromagnetic wave propagation in a medium with defects

The equations of the electromagnetic field in a solid with defects were obtained and an approximate wave solution was found by the Debye–Rytov method.     

Configuration of normal vibrations in an unbounded medium containing dislocations with allowance for energy dissipation

On the basis of the calibration model of plastically incompressible medium with dissipation we consider the structure of vibrations in an unbounded medium with dislocations. Inclusion of dissipation of weakly damped low-frequency vibrations of volume contraction and high-frequency longitudinal sound vibrations is shown to cause a considerable change in the structure of normal vibrations. For a certain dissipation weakly damped low-frequency vibrations of volume contraction and high-frequency longitudinal sound vibrations are described by one branch of the dispersion relation. The structure of the vibrations changes from liquid-like vibrations to longitudinal sound vibrations in the neighborhood of , which together with the boundary frequency ₀ of optical vibrations is characteristic. The calibration model including energy dissipation does not describe the Cosser liquid.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 40–44, March, 1995.     

Attenuation of pulsed CO2 laser radiation in an argon medium containing fine aluminum particles

The attenuation of 10.6-μm radiation by aluminum aerosol particles dispersed in argon is studied experimentally. An optimal method of forming the initiating beam is found. The size and concentration of fine Al particles in the medium are estimated.     

Pulsed ytterbium-doped large mode area double-clad fiber amplifier in MOFPA configuration

A pulsed master oscillator fiber power amplifier working in nanosecond range has been developed. An ytterbium-doped double-clad (large mode area) optical fiber was used as an amplifying medium. Actively Q-switched Nd:YVO laser was used as a seed of light pulses. The system worked at the repetition rate from 10 kHz to 40 kHz. At the amplifier output, pulses of 10.9 kW peak-power were achieved. The laser system worked at the slope efficiency of 30%.     

Reduced critical rotation for resistive-wall mode stabilization in a near-axisymmetric configuration

Recent DIII-D experiments with reduced neutral beam torque and minimum nonaxisymmetric perturbations of the magnetic field show a significant reduction of the toroidal plasma rotation required for the stabilization of the resistive-wall mode (RWM) below the threshold values observed in experiments that apply nonaxisymmetric magnetic fields to slow the plasma rotation. A toroidal rotation frequency of less than 10 krad/s at the q=2 surface (measured with charge exchange recombination spectroscopy using C VI) corresponding to 0.3% of the inverse of the toroidal Alfvén time is sufficient to sustain the plasma pressure above the ideal MHD no-wall stability limit. The low-rotation threshold is found to be consistent with predictions by a kinetic model of RWM damping.     

Higher order mode laser beam scintillations in oceanic medium

Abstract

In a horizontal oceanic optical wireless communication link, the scintillation index (the measure for the intensity fluctuations) of the received intensity caused by the oceanic turbulence is formulated and evaluated when the source is a higher order mode laser. Variations in the scintillation index vs. the underwater turbulence parameters, size of the higher order mode laser source, link length, and the wavelength are examined. Underwater turbulence parameters are the ratio that determines the relative strength of temperature and salinity in driving the index fluctuations, the rate of dissipation of the mean squared temperature, the rate of dissipation of the turbulent kinetic energy, and the Kolmogorov microscale length.