Scattering characteristics of a beam mode in a dielectric-slab optical waveguide. Part II

The radiated power of scattered light caused by refractive-index inhomogeneities and waveguide wall irregularities in an asymmetric slab waveguide is investigated by using the stationary phase method on the basis of a first-order perturbation theory. The correlation between both imperfections of the refractive index and the waveguide wall is taken into consideration. It is found that the correlation between both imperfections hardly affects the radiated power caused by air radiation modes while it modifies the radiated power caused by substrate radiation modes.     

Study of the topology of metal-containing granular films by light scattering and atomic force microscopy

The correlation properties of films consisting of granular structures with granules smaller than 6 nm prepared by the laser electrodispersion method are investigated. The correlation functions of the nanoparticle distribution on a transparent substrate are calculated from the angular structure of scattered radiation using the single-scattering approximation, as well as from the data of atomic force microscopy for copper, nickel, and palladium structures with different packing density. The size of coarse particles in nanostructures is estimated.     

Experimental attempt to detect stimulated “diffusion” scattering by particles in liquid

The change in the shape of the correlation function of the intensity of light scattered by particles in liquid, i.e., the appearance of a cosine component, with increasing excitation radiation intensity, is observed. The amplitude of this component increases with the intensity of exciting radiation. A quadratic component appears in the dependence of the scattering intensity on the exciting radiation intensity. These results point to the appearance of stimulated “diffusion” scattering by particle concentration fluctuations.     

Anomalous scattered light correlator

The space-time correlation function of the scattered radiation intensity of atoms situated in an external field is investigated. This function includes contributions of the normal +E^–> and anomalous –E–> complex field amplitude correlator. These correlators have components due to scattering by density fluctuations and to collective, diffraction effects. The spatial structure of these correlators is studied and the conditions for the measurement of the anomalous correlator are derived. The temporal properties of the anomalous correlator and the effect of Doppler broadening on the correlation properties of scattered radiation are also considered. The investigation of the anomalous correlator is of interest in high-resolution spectroscopy and may also be useful in the study of nonresonant media.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 70–73, February, 1982.     

Photon correlations in a multiple coherent and overlapping chaotic radiation field

We propose a study of the second-order coherence properties of radiation, such as inelastically scattered laser light, by performing an excess photon coincidence rate experiment a la Hanbury Brown-Twiss. The calculation evaluates the second-order correlation function of the electromagnetic field for an arbitrary number of coherent modes overlapped in phase space by a chaotic radiation field. We discuss the application of the general result to a specific case, namely the case of a single mode laser, and the Stokes radiation produced in a Brillouin-active medium, and a suitable part of the spectrum produced by causing dielectric breakdown in air.     

Three-dimensional diffuser and three-dimensional speckles

The well-known model of a diffusely scattering surface as a set of randomly distributed point scatterers is generalized to the case of a volume diffuser. Assuming that the coordinates of the coherent radiation source, the observer, and also the diffuser shape are arbitrary, a formula is obtained for the spatial correlation function of the scattered radiation intensity in a free field. Expressions to determine the transverse and longitudinal dimensions of the speckles are obtained for diffusers in the form of a rectangular parallelepiped and a cylinder. Zh. Tekh. Fiz. 68, 59–63 (December 1998)     

Gravitational scattering of electromagnetic radiation

The scattering of electromagnetic radiation by linearized gravitational fields is studied to second order in a perturbation expansion. The incoming electromagnetic radiation can be of arbitrary multipole structure, and the gravitational fields are also taken to be advanced fields of arbitrary multipole structure. All electromagnetic multipole radiation is found to be scattered by gravitational monopole and time-varying dipole fields. No case has been found, however, in which any electromagnetic multipole radiation is scattered by gravitational fields of quadrupole or higher-order multipole structure. This lack of scattering is established for infinite classes of special cases, and is conjectured to hold in general. The results of the scattering analysis are applied to the case of electromagnetic radiation scattered by a moving mass. It is shown how the mass and velocity may be determined by a knowledge of the incident and scattered radiation.This work was supported in part by the National Aeronautics and Space Administration and the National Science Foundation. It incorporates some of the results of the first author's doctoral dissertation at the University of Pittsburgh.     

Scattering contrast of X-ray radiation

It is experimentally established that, in the majority of cases, the X-ray radiation scattered on different constituent parts of a weakly absorbing object provides sufficient information on inner structure, different types of structural inhomogeneities, and morphological characteristics, such as shapes, sizes, and location of invisible defects of the object. In this study, a new method for investigation of the inner structure of noncrystalline materials is developed. The method is based on recording of the scattered X-ray radiation. It is demonstrated that the image contrast, formed by the X-ray radiation scattered on weakly absorbing objects, can be considerably higher than the absorption contrast.     

Streustrahlung von Silber durch Anregung von Oberflächenplasmaschwingungen

Socalled nonradiative surface plasma waves are excited in the visible spectral region by normal incidence of light on a rough surface of silver. By optical coupling by means of a prism they show up as scattered radiation, which is polarized parallel to the plane of emission. The scattered radiation can be excited by light polarized both parallel and perpendicular to the plane of emission. The dispersion of the surface plasma waves is worked out from the angular distribution of the scattered radiation.     

Reconstruction of the wind velocity profile from the intensity fluctuations of a reflected spherical wave in the turbulent atmosphere

The problem of reconstructing the wind velocity profile from the spatiotemporal statistics of turbulent reflected optical radiation intensity fluctuations is considered in the article. Expressions for the spatiotemporal correlation function and the spectrum of weak intensity fluctuations of the wave scattered on a diffusive screen are derived. An algorithm for reconstructing the wind velocity profile from the spatiotemporal spectra of the intensity of a reflected spherical wave in the turbulent atmosphere is suggested. The results of closed numerical experiments are presented that confirm the efficiency of the suggested algorithm.     

Condition of Retrieving Vertical Column Density of Atmospheric Pollution Gases by Using Scattered Solar Radiation

We present a method to monitor the vertical column density （VCD） of atmospheric pollution gases by using the scattered solar radiation. The necessary condition of capturing the useful scattered solar radiation is achieved. The condition is only dependent on the solar elevation angle, while independent of the solar azimuth angle, which could greatly simply the capturing equipment and procedure. Under the condition, the VCD of tropospheric NO2 in Chengdu, China is retrieved from the scattered solar radiation, which is close to that from the direct solar radiation.     

Threshold spectra of SBS at a finite frequency mismatch of the interacting waves

A problem of scattered radiation spectrum line width of stimulated Brillouin scattering (SBS) in plasma with two species of ions is considered. Threshold conditions, when SBS shifted frequency lines, which characterize the scattered radiation spectrum, are comparatively wide and are comparatively narrow, are defined. A possibility of existence of the scattered radiation spectrum with the frequency line width comparable to the ion-acoustic frequency is revealed.     

241Am-Be中子参考辐射的蒙特卡罗模拟研究

研究用于校准场所中子剂量监测仪表的241Am-Be中子参考辐射场计量特性。采用蒙特卡罗方法模拟了空气自由中子参考辐射(FRNR),GB/T 14055规定的最小尺寸中子参考辐射(SRNR)和实际中子参考辐射(ARNR)中不同检验点处中子周围剂量当量率、散射中子占比和能谱分布特征。研究结果表明,空气对FRNR中的剂量率和能谱分布影响小,近似为理想中子参考辐射;采用5%含硼聚乙烯作屏蔽的最小尺寸SRNR可减少热中子,降低散射中子占比,影锥法不适用于小尺寸中子参考辐射中对散射中子的修正;ARNR中的散射中子更少、占比更低,影锥法所得散射中子占比与理论值基本一致。     

激光同步辐射作为阿秒X射线辐射源的特性研究

 研究了逆流相对论电子与激光脉冲相互作用获得激光同步辐射的频率上移、微分散射截面等特性。发现逆流相对论电子与短脉冲激光相互作用，可以获得阿秒X射线辐射脉冲。短脉冲激光条件下得到的后向散射光的频率上移与长脉冲激光条件下得到的后向散射光的频率上移是完全一致的，同时发现随着入射电子初始能量的增加，散射光的准直性越来越好，后向散射光脉冲的脉宽越来越短。     

Measurement of the diffusion of anisotropic particles in an external field by the method of correlation spectroscopy

A method for studying the geometry of anisotropic particles based on the direct measurement of the components of the diffusion tensor of particles in an external field, is proposed. The value of the coefficient of diffusion is determined from the nature of the decay time of the correlation function of the intensity of the scattered radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 71–73, February, 1986.     

Three-dimensional generalization of the Van Cittert-Zernike theorem to wave and particle scattering

Coherence properties of primary partially coherent radiations (light, X-rays and particles) elastically scattered from a 3D object consisting of a collection of electrons and nuclei are analyzed in the Fresnel diffraction region and in the far field. The behaviour of the cross-spectral density of the scattered radiation transverse and along to the local direction of propagation is shown to be described by respectively the 3D Fourier and Fresnel transform of the generalized radiance function of a scattering secondary source associated with the object. A relativistic correct expression is derived for the mutual coherence function of radiation which takes account of the dispersive propagation of particle beams in vacuum. An effect of the spatial coherence of radiation on the temporal one is found; in the Fresnel diffraction region, in distinction to the field, both the longitudinal spatial coherence and the spectral width of radiation affect the longitudinal coherence. A solution of the 3D inverse scattering problem for partially coherent radiation is presented. It is shown that squared modulus of the scattering potential and its 2D projections can be reconstructed from measurements of the modulus and phase of the degree of transverse spatial coherence of the scattered radiation. The results provide a theoretical basis for new methods of image formation and structure analysis in X-ray, electron, ion, and neutron optics.     

Selective reflection of resonance radiation from excited media

According to quantum electrodynamics, the cross section for resonant scattering of radiation on an aggregate of excited atoms can be written as a sum of positive definite terms. This type of structure is not consistent with the Fresnel formulas for the reflection coefficient of radiation from thermally excited media. The difference shows up on a macroscopic level and indicates that semiclassical radiation theory cannot be used. A study of the correlation between elastic scattering and stimulated emission processes clarifies the reason for the discrepancies. The resulting singularities require summing of Feynman diagrams which appear beginning in the sixth order of perturbation theory. A lower bound estimate for the reflection coefficient from a plane layer is given, including processes which violate the statistics of radiation. The contribution of stimulated emission processes caused by the initially scattered photon are examined specifically. An experiment is proposed which would settle the choice of theories. Zh. éksp. Teor. Fiz. 113, 521–538 (February 1998)     

Method for Describing the Angular Distribution of Optical Radiation Scattered by a Monolayer of Ordered Spherical Particles (Normal Illumination)

We have developed a method for describing the angular distribution of intensity of radiation scattered by a monolayer of homogeneous spatially ordered monodisperse spherical particles normally illuminated by a plane circularly polarized electromagnetic wave. The method is based on the quasicrystalline approximation (QCA) of the theory of multiple scattering of waves (TMSW) using the multipole expansion of fields and the tensor Green function in vectorial spherical wavefunctions. The method is applied for analyzing the characteristics of radiation scattered by a partially ordered monolayer and a monolayer with a nonideal lattice. The results of calculations are compared with the available experimental data on the position of the first-order diffraction peak on the angular and spectral dependences of the intensity of radiation scattered by a closely packed monolayer with a nonideal triangular lattice of SiO₂ particles. Good conformity of the results has been established.     

Scattering of CO2 laser beam by a plasma of air breakdown at pressures of 1–300 torr

Results from experiments with a TEA CO₂ laser with an unstable cavity and a power of 10⁷ W are presented. Laser radiation was focused by a lens with a focal length of 100 or 150 mm in air free of dust (grains larger than 0.1 μm were filtered out). The power and energy of radiation scattered within a central cone of an annular laser beam was recorded. The dependences of the threshold (for scattering) laser power and the scattered power on pressure were determined. The angular divergence of the collimated scattered beam was found to be 3.9 mrad, which was close to the divergence of the laser beam (2.5 mrad). The amplification of the scattered radiation pulse was performed.     

Skin as a transformer of the polarization structure of laser radiation

Transformation of the polarization structure of a laser radiation scattered by the human skin is studied. A technique based on the matrix modeling of the optical properties of the skin considered as a superposition of epidermis and dermis, is proposed. Physical mechanisms behind the transformation of the polarization state of the scattered laser radiation are analyzed in terms of the ensemble of biospeckles.