Enhanced scattering from a thin film with one-dimensional disorder

This paper deals with a TE plane wave scattering from a thin film with one-dimensional disorder by means of the stochastic functional approach. The thin film is one-dimensionally inhomogeneous in the horizontal direction with infinite extent, and is homogeneous in the vertical direction with finite thickness. Based on an approximate wavefield representation in terms of a Wiener-Hermite expansion in a preceding paper (Tamura et al., 2004, Waves in Random Media, 14, 435-465), the first- and second-order incoherent scattering cross-sections are presented in explicit forms and scattering properties are discussed. The scattering properties vary entirely with the film thickness. In a case where the thickness is smaller than a few wavelengths in the thin film, enhanced scattering and associated enhanced scattering may appear as sharp peaks or dips on the second-order incoherent scattering distribution if the thin film has guided wave modes. When the thickness becomes sufficiently larger than the wavelength inside the film, a new enhanced scattering phenomenon appears as gentle peaks on the second-order incoherent scattering distribution in four special directions. Such four directions are the directions of forward scattering, specular reflection, backscattering, and the symmetrical direction of forward scattering with respect to the normal of the film surface.The first-order incoherent scattering occurs distinctly in four such directions. Such enhanced scattering is independent of the existence of the guided wave modes inside the thin film, and deeply relates to the structure of the thin film with one-dimensional disorder that has infinite correlation in the vertical direction. For SiC and glass thin films having one-dimensional disorder with a Gaussian correlation and three types of exponential correlation, the first- and second-order incoherent scattering cross-sections are illustrated in figures. The narrow enhanced scattering peaks appear for the glass film in a thin case. The gentle enhanced peaks turn up for both the SiC and glass films in a thick case. Furthermore, the optical theorem is calculated for several cases. It is then found that the error of the optical theorem decreases and the performance of the wavefield is improved by taking into account the second-order incoherent scattering.     

Enhanced scattering from a thin film with one-dimensional disorder

This paper deals with a TE plane wave scattering from a thin film with one-dimensional disorder by means of the stochastic functional approach. The thin film is one-dimensionally inhomogeneous in the horizontal direction with infinite extent, and is homogeneous in the vertical direction with finite thickness. Based on an approximate wavefield representation in terms of a Wiener–Hermite expansion in a preceding paper (Tamura et al., 2004, Waves in Random Media, 14, 435–465), the first- and second-order incoherent scattering cross-sections are presented in explicit forms and scattering properties are discussed. The scattering properties vary entirely with the film thickness. In a case where the thickness is smaller than a few wavelengths in the thin film, enhanced scattering and associated enhanced scattering may appear as sharp peaks or dips on the second-order incoherent scattering distribution if the thin film has guided wave modes. When the thickness becomes sufficiently larger than the wavelength inside the film, a new enhanced scattering phenomenon appears as gentle peaks on the second-order incoherent scattering distribution in four special directions. Such four directions are the directions of forward scattering, specular reflection, backscattering, and the symmetrical direction of forward scattering with respect to the normal of the film surface.The first-order incoherent scattering occurs distinctly in four such directions. Such enhanced scattering is independent of the existence of the guided wave modes inside the thin film, and deeply relates to the structure of the thin film with one-dimensional disorder that has infinite correlation in the vertical direction. For SiC and glass thin films having one-dimensional disorder with a Gaussian correlation and three types of exponential correlation, the first- and second-order incoherent scattering cross-sections are illustrated in figures. The narrow enhanced scattering peaks appear for the glass film in a thin case. The gentle enhanced peaks turn up for both the SiC and glass films in a thick case. Furthermore, the optical theorem is calculated for several cases. It is then found that the error of the optical theorem decreases and the performance of the wavefield is improved by taking into account the second-order incoherent scattering.     

Conductance of a perfect thin film with diffuse surface scattering

The conductance of thin films with diffusive surface scattering was solved semiclassically by Fuchs and Sondheimer. However, when the intrinsic electron mean free path is very large or infinite their conductance diverges. In this Letter a simple diffraction picture is presented. It yields a conductance which corresponds to a limiting mean free path of a(2)/lambda(F), where a is the film thickness.     

Electron-ripplon scattering for a thin film of liquid helium

The mobility of electrons governed by an electron-ripplon scattering is calculated for finite thickness of He films.     

Scalar particle with polarizability in the field of a plane electromagnetic wave and in an electric field

Exact solutions are obtained for the wave equations for a scalar particle that possesses polarizability in the field of a plane electromagnetic wave of arbitrary polarization and in a constant electric field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 40–43, February, 1991.     

Elastic scattering amplitude of a scalar particle in a plane wave field

The elastic scattering amplitude of a scalar particle in an arbitrary plane wave electromagnetic field is obtained in the form of a double integral by the method of dispersion relations. Particular cases of giving the plane wave field are investigated. It is shown that the existence of scalar particle radiation in an arbitrary plane wave electromagnetic field results in elastic scattering, whose amplitude determines the change in particle mass in this field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 32–37, May, 1990.     

Truncating cylindrical wave modes in two-dimensional multiple scattering

When analyzing the two-dimensional multiple scattering of electromagnetic waves by cylinders, the incident, scattered, and transmitted fields need to be represented by infinite sums of cylindrical wave modes. These infinite sums need to be truncated to a finite limit in order to calculate the scattering matrix. The accuracy of the scattered field representation and the stability of the matrix inversion are both critically dependent on the truncation limit. The parameters involved in the scattering are analyzed to determine their effect on the upper and lower bounds of an appropriate modal truncation.     

Raman scattering for lead telluride-based thin film structures

For single-crystal epitaxial lead telluride films, Raman spectra obtained under conditions in which the intensity of incident radiation is minimized in order to suppress photo-initiated oxidative process are presented. The spectra were measured with an InVia Renishaw spectrometer at an exciting radiation wavelength of 514.5 nm and in-line focusing of a 20-μW beam. These measuring conditions allowed us for the first time to experimentally observe a large set of peaks for lead telluride, the positions of which were in line with the theoretical values of harmonics and combinatorial PbTe phonon modes. In order to demonstrate the possibilities of the methodology used, the picture of phonon modes for single-crystal and polycrystalline films of the Pb_{1 ? x} Eu _x Te (0.05 ? x ? 0.10) solution was additionally considered.     

Multiple scattering of an obliquely incident plane acoustic wave from a grating of immersed cylindrical shells

The study of the interaction of acoustic waves with cylindrical structures has numerous applications including the ultrasonic nondestructive testing of materials. In this paper, using a new mathematical model presented for the scattering of obliquely incident plane acoustic waves from a grating of immersed cylindrical shells, a detailed study of the resonant interaction of A-wave resonances originating from the shells is conducted. The nature of A-wave resonances and the effect of center-to-center distance of the shells on these resonances are examined. It is observed that this resonant interaction not only results in the splitting of A-wave resonances, but also causes an increase in resonance amplitudes. This interaction phenomenon is not seen in Rayleigh, whispering gallery and guided wave resonances. It is also shown that increasing the angle of wave incidence to the grating weakens the A-wave resonant interactions. The numerical results obtained from the mathematical model are compared to experimental results available in the literature for gratings composed of two and three aluminum shells. The numerical results are in very good agreement with their experimental counterparts.     

Correlation of fluctuation field and temperature coefficient of coercivity in a CoCrPtB thin film

The effect of the ratio of fluctuation field (H_f) to coercivity (H_c) on the temperature coefficient of coercivity [α(H_c)] was investigated for Co₅₅Cr_15.5Pt₂₈B_1.5/Co₆₃Cr₃₇/Cr, Co₆₉Cr₁₉Pt₉Ta₃/Cr, and Co₈₆Cr₁₀Ta₄/Cr thin films (longitudinal recording media) with very small average grain volume (V_phy). α(H_c) increases markedly with increase in temperature between near 250 and 350 K for Co₅₅Cr_15.5Pt₂₈B_1.5/Co₆₃Cr₃₇/Cr thin films. α(H_c) is approximately proportional to the ratio H_f/H_c for all thin films, as in the case of advanced data backup tapes prepared from ultrafine particles. α(H_c) and the ratio H_f/H_c increase as V_phy decreases. Smaller H_f/H_c values are necessary for small α(H_c) values, which is very important for the thermal stability of high-density recording media with very small V_phy.     

The gain of the stimulated scattering of a two-dimensional localized pumping wave at arbitrary scattering angles

The problem of the stimulated scattering of a two-dimensional localized pumping wave is considered. The dependence of the spatial gain on the angle of scattering and intensity of pumping is found. Interpretation of this gain is given at arbitrary relationships between the free path of the sound wave and transverse dimension of the interaction domain.     

Reflection of a spherical wave from a plane surface

A simple approach to the reflection of a spherical sound wave from a locally reacting plane surface is developed. The theory is based on a generalization of the method of images, and expresses the reflected wave as a series in terms of the reciprocal of distance from the image source. Although no general proof that this form for the reflected wave satisfies the surface boundary condition to all orders is available, it has been shown that the first five terms of this solution does satisfy the boundary condition, and agrees with the existing exact solutions for this type of reflection.     

Distinctive features of a pulsed beam scattering on a plane surface (two-dimensional case)

A two-dimensional problem of scattering of pulsed beams having arbitrary time and spatial form on a plane surface of a lossy dielectric halfspace is solved. A pulsed beam has been modeled by letting an E- or H-polarized plane pulse with homogeneous front pass through a space filter. The reflected pulse is found using an expansion of the incident pulsed beam over time-harmonic plane waves.     

Numerical study of a thin liquid film flowing down an inclined wavy plane

We investigate the stability of a thin liquid film flowing down an inclined wavy plane using a direct numerical solver based on a finite element/arbitrary Lagrangian Eulerian approximation of the free-surface Navier-Stokes equations. We study the dependence of the critical Reynolds number for the onset of surface wave instabilities on the inclination angle, the waviness parameter, and the wavelength parameter, focusing in particular on mild inclinations and relatively large waviness so that the bottom does not fall monotonously. In the present parameter range, shorter wavelengths and higher amplitude for the bottom undulation stabilize the flow. The dependence of the critical Reynolds number evaluated with the Nusselt flow rate on the inclination angle is more complex than the classical relation (5/6 times the cotangent of the inclination angle), but this dependence can be recovered if the actual flow rate at critical conditions is used instead.