Toward superlensing with metal–dielectric composites and multilayers

We report on the fabrication of two types of adjustable, near-field superlens designs: metal–dielectric composites and metal–dielectric multilayer films. We fabricated a variety of films with different materials, thicknesses and compositions. These samples were characterized physically and optically to determine their film composition, quality, and optical responses. Our results on metal–dielectric composites indicate that although the real part of the effective permittivity generally follows effective medium theory predictions, the imaginary part does not and substantially higher losses are observed. Going forward, it appears that multilayer metal–dielectric designs are more suitable for sub-diffraction imaging applications because they could provide both tunability and low loss.     

Reflection and refraction of light by a system of interfering atomic states

The boundary problem of nonlinear optics was investigated for a trial wave reflected (refracted) by an excited region of a nonlinear medium considered as a system of multilevel atoms in the spectrum of which there are two closely-spaced energy levels excited by a powerful quasi-resonant radiation. It is shown that under interference conditions of the atomic states in the field of the trial and resonance waves there exist three types of waves: an inverse wave and two polarization waves. By way of extension of the Ewald-Oseen procedure to this case a formula for the complex refractive index of a nonlinear medium for the three types of waves as well as a generalized extinction theorem have been obtained. It is shown that the trial wave can be amplified without inversion of the interfering atomic states and that the refractive index can be markedly changed at certain concentrations of atoms in the medium. General formulas for the amplitudes of the reflected and refracted waves have been obtained. Ul’yanovsk State University, 42, Tolstoi Str., Ul’yanovsk, 432700, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 568–575, July–August, 1998.     

On the kinetic theory of energy losses in a randomly heterogeneous medium

The equation describing the distribution of energy losses of a particle propagating in a fractal medium with quenched and dynamic heterogeneities has been derived. It has been shown that in the case of the medium with fractal dimension 2 < D < 3, the losses Δ are characterized by the sublinear anomalous dependence Δ ∼ x ^α with a power-law dependence on the distance x from the surface and exponent α = D − 2.     

Energy losses of dipoles traveling relative to a moving medium

We consider the radiation from nonoscillating dipoles traveling with constant velocity directed parallel or antiparallel to the velocity of a homogeneous transparent moving medium. It is assumed that the medium in its rest frame is isotropic and has no spatial dispersion. We obtain expressions for the radiative energy losses and estimate the polarization energy losses of electric and magnetic dipoles of different orientations. In particular, it is shown that the energy loss of a source is negative if it moves in the direction of the medium motion and the source velocity is less than the medium velocity. Estimates for the energy losses of dipoles in the cases of an electron beam and a flow of a weakly dispersive medium are given. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 6, pp. 502–512, June 2006.     

Heavy-tailed distribution of cyber-risks

With the development of the Internet, new kinds of massive epidemics, distributed attacks, virtual conflicts and criminality have emerged. We present a study of some striking statistical properties of cyber-risks that quantify the distribution and time evolution of information risks on the Internet, to understand their mechanisms, and create opportunities to mitigate, control, predict and insure them at a global scale. First, we report an exceptionnaly stable power-law tail distribution of personal identity losses per event, Pr(ID loss ≥ V) ~ 1/V^b, with b = 0.7 ± 0.1. This result is robust against a surprising strong non-stationary growth of ID losses culminating in July 2006 followed by a more stationary phase. Moreover, this distribution is identical for different types and sizes of targeted organizations. Since b < 1, the cumulative number of all losses over all events up to time t increases faster-than-linear with time according to ≃ t^1/b, suggesting that privacy, characterized by personal identities, is necessarily becoming more and more insecure. We also show the existence of a size effect, such that the largest possible ID losses per event grow faster-than-linearly as ~S^1.3 with the organization size S. The small value b ≃ 0.7 of the power law distribution of ID losses is explained by the interplay between Zipf’s law and the size effect. We also infer that compromised entities exhibit basically the same probability to incur a small or large loss.     

Calculations,in the three-dimensional approximation,for a half-symmetric unstable resonator with internal axicon (HSURIA) in the three-dimensional diffraction approximation with annular shape of the active medium

6. Conclusions 1. It was shown that, compared with other methods, realization of the analytic Prony method increases strongly the effective establishment of the radiation of the mode structure of the radiation field in an empty cavity having o complex configuration, such as the HSURIA resonator. 2. We investigated the dependence of the losses of various azimuthal and radial modes in an empty HSURIA resonator on the value of N_eq. We have shown that in the region N_eq=20−25 and at M=2 the losses of the highest-Q zeroth and first azimuthal modes amount to ≈0.65 and ≈0.70 respectively, which ensures lasing in the single-mode regime in the case of a sufficiently homogeneous active medium. 3. We found the field distributions of various azimuthal and radial modes in the HSURIA resonator in the absence of a medium. 4. We have shown that in the case of lasing on one highest-Q mode the radiation intensity on the tip of a W-axicon is not more than 2–3 times larger than the average over the central region of the W-axicon. Translated from Preprint No. 31 of the Lebedev Physics Institute, Russian Academy of Sciences, Moscow, 1991.     

Negative index materials with gain media for fast modulation

Negative index materials (NIM) enable subwavelength resolution and are promising for applications in integrated optical systems, since the mode volume is small. Most promising NIM systems essentially use noble metals (Ag, Au) with material losses much lower than in other metals, but still rather hefty, like in metal–dielectric–metal “fishnets”. Therefore, we perform extensive finite-difference time-domain modeling of NIM “fishnets” in combination with gain medium, InGaAsP multiple quantum wells in the present work. The signal recovery is weak, which is related to weak overlap between the radiation field and the gain medium. The signal modulation speed may be very large, in a picosecond range.     

Time-domain, nuclear-resonant, forward scattering: theclassical approach

This paper deals with the interaction of electromagnetic radiation with matter assuming the matter to have nuclear transitions in resonance with incident electromagnetic radiation. The source of the radiation is taken to be of two types; natural radioactive gamma decay and synchrotron radiation. Numerical examples using ⁵⁷Fe are given for the two types of source radiation. Calculated results are contrasted for the two cases. Electromagnetic radiation produced by recoil-free gamma-ray emission has essentially the natural linewidth. Electromagnetic radiation from a synchrotron, even with the best monochromators available, has a relatively broad-band spectrum, essentially constant for these considerations. Polarization effects are considered. In general, the nuclear-resonant medium changes the polarization of the input radiation on traversing the medium. Calculations are presented to illustrate that synchrotron radiation studies using nuclear-resonant forward scattering have the potential for making high-precision measurements of hyperfine fields and recoilless fractions. An interesting aspect of nuclear-resonant forward scattering, relative to possible gamma-ray laser development, is the so-called “speed-up” effect. This revised version was published online in August 2006 with corrections to the Cover Date.     

Optical properties of grooved silicon microstructures: Theory and experiment

The reflection spectra of grooved silicon structures consisting of alternating silicon walls and grooves (air channels) with a period of a = 4–6 μm are studied experimentally and theoretically in the mid-IR spectral range (2–25 μm) upon irradiation of samples by normally incident light polarized along and perpendicular to silicon layers. The calculation is performed by the scattering matrix method taking into account Rayleigh scattering losses in a grooved layer by adding imaginary parts to the refractive indices of silicon and air in grooved regions. The experimental and calculated reflection spectra are in good agreement in the entire spectral range studied. The analysis of experimental and calculated spectra gave close values of the effective refractive indices and birefringence of the studied structures in the long-wavelength spectral region. The values calculated in the effective medium model in the long-wavelength approximation (λ ≫ a) gave considerably understated values. The obtained results confirm the efficiency of the scattering matrix method for describing the optical properties of silicon microstructures.     

Diffraction by a corrugated interface of media: The influence of the corrugation shape and losses in the medium on total transformation regimes

We study regimes of total reflection of a plane wave to the diffraction lobe in the case where the wave is incident on a corrugated metal surface or a corrugated interface of two dielectric media. The purpose is to analyze the influence of both the corrugation shape and losses in the medium on the characteristics of the regimes of total reflection to the diffraction lobe. We consider a number of corrugation profiles differing from the sinusoid by the resonance-region width and the presence of additional elements, namely, (i) the profiles having pair resonance regions with scale of the order of the wavelength, for which qualitatively new diffraction regimes compared with those observed for the sinusoidal interface can be realized due to interaction of waves, and (ii) the profiles comprising small-scale deviations, which can be a model of actual gratings. To study the influence of losses in the problem of scattering from a corrugated interface of dielectrics, the dielectric permittivity is assumed complex. We compare the obtained results with data for a sinusoidal profile and loss-free media. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 5, pp. 391–405, May 2006.     

Response of thin polymer layers confined between solid surfaces and submitted to normal oscillatory deformations

Summary The viscoelastic properties of liquids close to solid surfaces differ from the bulk. Nanorheology has been performed by using a surface force apparatus adapted to operate as a rheometer in a sphere-plane geometry. Axial oscillatory measurements have been carried out with high polymer solutions filling the gap. The deformations were kept sufficiently small not to perturb the film structure and were applied in a large range of frequency (10⁻³ to 10² s⁻¹). It is shown that the complex modulus characterizing the confined medium can be split into two components: a shear modulus (it accounts for the viscous dissipation due to the flow of solvent molecules through the mesh created by the long polymer chains which connect the two solid surfaces) and a compression modulus which is related to the normal stress response of the chains confined between the solid surfaces. The hydrodynamic screening lengthξ _h and the correlation length ξ deduced from the two moduli are compared and are found to scale in the same way as a function of the distance between the two surfaces. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Radiation of extended electromagnetic sources moving near the surface of a chiral medium

Current-carrying and charged filaments moving in vacuum along the plane surface of a semiinfinite chiral medium are investigated. The electromagnetic fields and energy losses due to radiation are found in both cases. The dependence of the radiation losses on the chirality constant is given. State Electrotechnical University of St. Petersburg, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 7, pp. 866–873, July, 1998.     

Whistler waves guided by ducts with enhanced density in a collisional magnetoplasma

We study the guided propagation of whistler waves along cylindrical ducts with enhanced density in a collisional magnetoplasma. It is shown that under certain conditions, the presence of comparatively small dissipative losses due to electron collisions in a plasma medium can lead to significant changes in the dispersion characteristics and field structures of whistler modes guided by such ducts compared with the case of a collisionless plasma. We present the results of numerical calculations showing such changes in the properties of whistler modes. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 1, pp. 31–49, January 2008.     

Optical properties of BiB3O6 with different phase matching orientations

Basic optical properties of the new nonlinear crystal BiB₃O₆ (BIBO) are measured for second harmonic generation (SHG) of 1064 nm radiation. These properties include the effective nonlinearities for different phase matching orientations, the corresponding acceptance bandwidths and the optical losses. Effective nonlinearities of up to 3.2 pm/V (ϕ=90°, θ=-11°) and losses of less than 0.1 %/cm at 1064 nm indicate that BIBO is a promising new nonlinear crystal for SHG of 1064 nm radiation. A two-dimensional measurement with high spatial resolution of the SHG efficiency and the optical homogeneity, clearly demonstrate the high optical quality of BIBO crystals now available. PACS 42.65.Ky; 42.70.Mp     

Chemistry in space

Summary Molecules have been observed in widely disparate astronomical objects, from comets to supernova remnants. Interstellar space appear to be a real chemical laboratory, able to produce a large number of molecules, some of them relatively complex. The abundances show a very high sensitivity to local physical properties and dynamical history. This sensitivity renders molecular observations and astrochemical modelling very flexible tools for investigating the properties and evolution of the interstellar medium. A brief outline of morfology of interstellar medium is given, together with a discussion of the basic chemical processes leading to the molecular formation. Since interstellar-dust particles play a crucial role in the chemical evolution of interstellar medium, physical and chemical properties of dust are reviewed. Finally, by way of an example of modelling exercise, a toy model of the chemical evolution of interstellar gas is presented. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Metallic negative index nanostructures at optical frequencies: losses and effect of gain medium

One of the most important modern problems in modern electromagnetics is a design and study of negative index metamaterials that may enable sub-wavelength imaging at optical frequencies. Plasmonic periodic metal-dielectric nanostructures present one interesting possibility for both 2D and 3D negative index medium (NIM) systems. The displacement current near plasmonic resonance excitations may produce both negative permittivity and negative permeability (most difficult) in a NIM with e.g. “fishnet” metal-dielectric composite type structure. One obvious problem with a metallic NIM is that the response is strongly dispersive and lossy. Both of these effects are detrimental to sub-wavelength imaging. One way of mitigating losses is to use a gain medium. We address the question of sub-wavelength resolution in the fishnet NIM with and without gain medium. PACS 42.79.-e; 42.79.Dj; 42.81.Dp; 74.78.Fk; 78.66.Bz     

Singularity index of the electromagnetic field on the edge in the presence of the Veselago medium

The singularity index of the electromagnetic field on the edge of wedge structures of two types (with and without ideally conducting sides) is investigated in the presence of a sector of a medium with negative permittivity and permeability (the Veselago medium). Restrictions on the material and geometrical parameters at which the condition on the edge is violated are determined. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 56–58, August, 2006.     

Logic gate based on a one-dimensional photonic crystal containing quantum dots

The feasibility of using quantum dots as a dense resonant medium with large transition dipole moments is analyzed. The possibility of creating one-dimensional photonic crystals containing quantum dots is examined on the basis of published experimental and theoretical data and the basic parameters of such systems are discussed. A numerical solution of the generalized Maxwell–Bloch equations is used to show that the interaction of coherent light pulses with a photonic structure containing quantum dots can be used to create optical logical operations of types that will depend on the spectral properties of the crystal.     

Implications of an extended fractal hydrodynamic model

Considering that the motions of the particles take place on continuous but non-differentiable curves, i.e. on fractals with constant fractal dimension, an extended scale relativity model in its hydrodynamic version is built. In this approach, static (particle in a box and harmonic oscillator) and time-dependent (free particle etc.) systems are analyzed. The static systems can be associated with a coherent fractal fluid (of superconductor or of super-fluid types behavior), whose particles are moving on stationary trajectories. The complex speed field of the fractal fluid proves to be essential: the zero value of the real (differentiable) part specifies the coherence of the fractal fluid, while the non-zero value of the imaginary (non-differentiable or fractal) part selects, through some “quantization” relations, the “stationary” trajectories (that may correspond to the observables from quantum mechanics) of the fractal fluid particles. Moreover, the momentum transfer in the fractal fluid is achieved only through the fractal component of the complex speed field. The free time-dependent systems can be associated with an incoherent fractal fluid, and both the differentiable and fractal components of complex speed field are inhomogeneous in fractal coordinates due to the action of a fractal potential. It exist momentum transfer on both speed components and the “observable” in the form of an uniform motion is generated through a specific mechanism of “vacuum” polarization induced by the same fractal potential. The analysis on the fractal fluid specifies conductive properties in the case of movements synchronization both on differentiable and fractal scales, and convective properties in the absence of synchronization.