Polarization Of Incident Radiation Research Articles

Statistics of local field intensity enhancements at nanostructured surfaces investigated with a near-field optical microscope

Near-field intensity distributions measured at nanostructured surfaces with a scanning near-field optical microscope are treated to determine the statistics of local field intensity enhancements. The probability density function (PDF) of the field intensity enhancement is calculated for surface-plasmon-polariton scattering by randomly rough surfaces of thin metal films and for light scattering in silver colloid fractals. We demonstrate that the statistics of the intensity distributions established in different scattering regimes, viz., single and multiple scattering, is distinctly different, and compare our results with the theoretical predictions available. We show that, in the regime of multiple scattering, the PDF decreases exponentially for large values of the intensity enhancement with the slope for surface-plasmon scattering being significantly different from that for light scattering in surface fractal structures. We also find that, in the latter case, the PDF slope is only weakly influenced by variations in the wavelength and polarization of incident radiation.

Anomalous polarization of Raman scattering by transverse and longitudinal phonons in porous doped GaAs

The Raman spectra of a porous doped GaAs(100) crystal were studied. It is established that emission in the plasma-phonon spectra of both the starting and porous crystals is highly polarized and is independent of the incident-radiation polarization. It is inferred that the contribution of the Froelich mechanism to the intensity of the plasma-phonon spectrum is predominant and that the effects of defects and multiple scattering on the scattered-light polarization in porous GaAs may be ignored. The cause for the violation of the selection rules in the spectrum of porous crystal is discussed.

The phenomenon of polarization suppression of X-ray Umweg multiple waves in crystals

The phenomenon of the polarization suppression of X-ray Umweg multiple waves in Renninger scans [Renninger (1937). Z. Kristallogr. 97, 107-121] of crystals, showing intensity decrease due to properly chosen wavelength and polarization of incident radiation, is observed. That is, one of the participating wave components in the multiple-wave interference is reduced considerably so that the intensity of multiple diffraction is decreased. The condition for total suppression of the multiple-wave interaction in crystals is derived theoretically from the Born approximation and verified with exact dynamical calculation and experiments. Partial suppression of the strong Umweg interfered component is demonstrated using elliptically or linearly polarized synchrotron radiation. The suppressed multiple-wave intensity distribution reveals high sensitivity to X-ray reflection phase. This multiple-diffraction technique under partial polarization suppression provides an alternative way of enhancing the visibility of multiple-wave interference in crystals for direct phase determination.

Kinetic Energies in the Direct Double Photoionization of Helium and the Electron-Electron Correlation

We present a simple model describing kinetic energy probability distributions of outgoing electrons in the direct double photoionization of helium. The model applies to photons of energy greater than the binding energy of the atom and to radiation intensities extending from perturbation regime to the strong-field one. It appears that the shape of probability distribution is mainly determined by the electron-electron correlation in their final state. For nonperturbative intensities the distribution depends strongly on polarization of incident radiation.

Optical activity and dichroism in □CdGa2S4

The first observation of optical activity and circular dichroism in the defect chalcopyrite semiconducting compound □CdGa2S4 is reported. Optical absorption spectra were recorded at 300 and 25 K under non-polarised radiation as well as under different directions of polarisation of incident radiation. In the transparent region (400–900 nm) the optical absorption depends strongly on the direction of polarisation, confirming that □CdGa2S4 is a dichroic crystal. Therefore it is an ideal material as a sensor for polarised radiation. Copyright © 1999 John Wiley & Sons, Ltd.

Light extinction by two finite parallel dielectric cylinders

The VIEF (volume integral equation formulation) method is used to calculate the distribution of fields in two parallel dielectric cylinders and to determine the scattering characteristics of one particle in the presence of another. The numerical calculations performed have revealed that the curve of the extinction efficiency of one cylinder in the presence of another versus the distance between the cylinders axes behaves like damped oscillations. An analysis is made of the influence of the size and shape of the particles and their relative refractive index as well as of the state of incident radiation polarization on the limiting—for manifestation of optical integration of particles—distance leff.

Three-Beam Diffraction in Finite Perfect Crystals. II. Influence of Absorption, Resonant Scattering and Polarization

By using the boundary-value Green-function technique, effects of absorption, resonant scattering and polarization are incorporated in the solution of the Takagi–Taupin equations for three-beam diffraction in finite perfect crystals. It is shown how such features may influence the dynamical interactions. The potential of three-beam interference acting as a phase-sensitive probe for resonant scattering is demonstrated. Depending on the applied model used for the calculations of the corrections to the atomic scattering factor, profile asymmetry reversal is theoretically predicted to occur near the photoelectric threshold in a finite germanium crystal. Significant distortions of the three-beam profiles are found for polarized incident radiation, especially for reflection triplets having an invariant phase sum near 90°.

Polarization characteristics of non-Gaussian scattering by small particles

Abstract The statistical properties of radiation which has been singly scattered by a finite number of small spheroidal particles are investigated. Single-particle fluctuation enhancement factors are calculated for a variety of incident radiation polarization states and it is shown that full probability densities can be expressed in closed form in some situations of interest. Results for both free-particle assemblies and surface deposits are presented.

Modification of a strong resonance radiation polarization in media with Doppler-broadened transitions of 0 to 1 and 1 to 0 types and in the presence of a DC electric field

For atomic media with resonant Doppler-broadened transitions of J=0 to J'=1 or J=1 to J'=0 type and taking into account the relaxation due to depolarizing collisions, a theory of non-linear optical polarization phenomena in the presence of a DC electric field is developed. The theory is valid in the case of both arbitrary resonance radiation intensity and arbitrary external DC electric field spatial orientation. The intensity-dependent contributions to variation of radiation polarization are analysed in detail in the Doppler limit. Special attention is paid to the case of linear polarization of incident radiation; in this case as well as in the presence of a DC electric field, the Doppler-enhanced non-linear optical contributions determining the emerging ellipticity and the rotation angle of polarization, respectively, are of the same order of magnitude (unlike the case of external magnetic field, in which the key effect is the rotation of polarization). It is shown, however, that in the case of the strictly transverse geometry and if the angle between the electric field direction and the initial polarization vector is equal to 45 degrees , the Doppler-enhanced non-linear optical contribution to the rotation angle becomes anomalously small. The effect of the presence of a longitudinal component of electric field on the non-linear optical polarization phenomena is investigated. In addition, although in the case of a purely longitudinal geometry for the considered transitions the electric field effect on radiation polarization modification is absent, some analytic results concerning self-rotation and deformation of a polarization ellipse in the Doppler limit for an intense initially elliptically polarized radiation are also presented.

Linear polarization and the effects of metal reflectors used to redirect the beam in microwave radiometers

Problems concerning the response of microwave radiometers to the polarization of incident radiation are examined. Particular attention is given to their consequences in experiments measuring the intensity anisotropy of the cosmic background radiation. Considered in detail are instrumental configurations in which metal reflectors are used to redirect the antenna beam. Some effects introduced by such reflectors are calculated and modelled for different values of some relevant parameters, in order to evaluate their contribution to instrumental errors. The analysis of a real experiment is then considered. It is shown that such mechanisms, if ignored, can seriously affect the measurements.

Photoionization of the hydrogen atom in a strong magnetic field

Abstract Photoionization of the hydrogen atom in a strong magnetic field (B ∼ 1011 – 1013G) is studied analytically and numerically for the ground and various excited atomic states and different polarizations of incident radiation.

Can the reflectivity of a nonlossy slab of arbitrary thickness loaded with a strip grating be identical to that of a plane interface over a wide range of frequencies?

Can the reflectivity of a nonlossy slab of arbitrary thickness loaded with a strip grating be identical to that of a plane interface over a wide range of frequencies? A negative response is provided to this question for broadside transverse magnetic polarized incident radiation. It is shown, however, that the strip-grating-loaded slab of thickness h > 0 has the same far-field response as the bare slab of thickness h at all frequencies. These conclusions are at odds with the recent results of Lakhtakia et al. [ J. Opt. Soc. Am. A3, 1788 ( 1986)] and also emphasize the nonuniqueness of the determination of a scattering structure from measurements, over a wide range of frequencies, of its far-field response to a plane wave at a fixed angle of incidence.

Inductive grids in the resonant region: Theory and experiment

We compare rigorous modal expansion methods with transmission-line models for the spectral properties of inductive grids. We compare the predictions of the former with measurements of grid transmittance, reflectance and phase angles as a function of wavelength. We show that the rigorous theory can accurately reproduce measured grid properties, both for normal and oblique incidence, and for both fundamental polarizations of incident radiation. We pay particular attention to the so-called “thickness dip”, an abrupt drop in transmittance which occurs for one polarization at off-normal incidence. We study the variation of\(\lambda _a\), the wavelength of the thickness dip, with grid parameters. We also study the variation of\(\lambda _m\), the wavelength of maximum transmittance, with grid parameters. We give four design rules which enable the optimization of grid parameters for use in multi-element filter stacks not relying on interference properties. We present a comprehensive set of curves showing the variation of spectral transmittance with grid aperture and thickness, for both fundamental polarizations and for a range of angles of incidence.

Rotation of plane of polarisation of a beam of microwaves by corrugated reflection surfaces

Corrugated metal surfaces show the property of rotatory polarisation. Orientation of the corrugations with plane of polarisation of incident radiation determines the extent of the tilt. The rotatory polarisation is additive when two corrugated reflecting surfaces are successively employed.

Polarization, spectral, and temperature characteristics of the photon drag effect in p-GaAs

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A reflection grating interferometer

A modal expansion formulation is presented to rigorously describe the diffraction from a perfectly conducting reflection grating in which each element consists of a rectangular cavity beneath a smaller rectangular aperture. For both S and P polarized incident radiation the structure is shown to exhibit spectacular resonance behaviour, similar to the interference phenomena obtained with a Fabry-Perot interferometer. A single-mode truncation of the theory is used to explain the action and show that for a Littrow mounting in the -1 order, 100% efficiency is achieved at resonance. The cavity depth and width determine the resonant wavelengths, while the narrow aperture width is found to be sensitively related to the positions and half-widths of the maxima.

Infrared reflection and dipole derivatives of azide ion in KN3

The infrared reflection spectrum of the 001 face of tetragonal KN3 has been studied between 100 and 2300 cm−1. Since an oblique incidence technique was employed, observations with TE polarized and TM polarized incident radiation allowed discrimination between crystal modes whose transition dipoles were parallel (A2u) or perpendicular (Eu) to the z axis. The reflection intensity was modeled by a classical harmonic oscillator formula for the dielectric constant, which associates three parameters with each mode. These parameters are νT, the transverse phonon frequency; S, the strength; and γ, the damping constant. From the value of S, taking into account the difference between external and internal effective fields, the values of the dipole derivatives ∂μ/∂q were determined for the several modes. These dipole derivatives were converted to internal coordinates, analyzed from the point of view of the effective charge–charge flux model, and compared with values found for the azide ion in NaN3.

Polarization and Angular Dependence of 1.06-μm Laser-Light Absorption by Planar Plasmas

An enclosing "box" calorimeter has been used to measure the polarization and angular dependence of 1.06-\ensuremath{\mu}m laser-light absorption under experimental conditions approximating those assumed by Estabrook, Valeo, and Kruer in their simulations; i.e., \ensuremath{\sim}${10}^{16}$ W/${\mathrm{cm}}^{2}$ plane waves incident on a planar plasma. A clear resonance absorption maximum was observed for $p$-but not for $s$-polarized incident radiation as predicted.

Directional dispersion of polar phonons measured by infrared reflection

AbstractThe dispersion of all polar optical phonons may be measured by the attenuated total reflection method. It is shown how the directional dispersion of the extraordinary polar phonons in uniaxial crystals is obtained in a similar way. In the (ω, k) diagram the areas of high reflectivity for transverse magnetic polarized incident radiation are determined by curves which have for k → 0 the same frequencies as extraordinary phonons propagating in an infinite crystal for k → ∞. At arbitrary crystal cuts these curves are boundaries for the existence of surface phonon‐polaritons. The method allows measuring the complete directional dispersion of t—t and l—l branches of Raman‐inactive polar phonons, too.

Multiphoton transitions. IV. Bound-free transition integrals in compact forms

For pt. III see abstr. A11153 of 1973. The basic integrals appearing in the N-photon T-matrix for ionization of neutral atoms and electron detachment of negative ions are obtained in compact forms both for circular polarization as well as for linear polarization of incident radiation. The present results circumvent the often lengthy procedure of summing the partial amplitudes and provide a basis for investigating physically interesting limits of multiphoton transitions, analytically.