Showing papers on "Total external reflection published in 2004"

Waveguiding in air by total external reflection from ultralow index metamaterials

Abstract: Metamaterials composed of metal-dielectric nanostructures can be engineered to have the real part of the effective refractive index less than unity at optical wavelengths. These materials show intriguing optical properties including total external reflection. We utilize this effect to design and analyze slab waveguide structures that guide visible light in an air core.

Astronomical soft x-ray mirrors reflectivity enhancement by multilayer coatings with carbon overcoating

Abstract: A number of X-ray astronomical missions of near future will make use of hard X-ray optics with broad-band multilayer coatings. However multilayer mirrors can be also useful to enhance the effective area of a given X-ray telescope in the "classical" low energy X-ray band (0.1 - 10 keV), the window where X-ray spectroscopy provides very useful plasma diagnostics) with a consistent gain with respect to usual single-layer reflectors. Multilayers for soft X-rays are based on stacks with constant d-spacing (in order to minimize the loss due to the photoelectric effect). A further gain in reflectivity (however only restricted to the energy range between 0.5 and 4 keV) can be achieved by using a low density material as a first external layer of the film, with the role of reducing the photoelectric absorption effect when the mirror acts in total external reflection regime (Carbon is the most performing material for this specific scope). In this paper the impact of using soft X-ray multilayer mirrors in future X-ray telescopes is discussed, and soft X-ray reflectivity tests performed on prototype samples presented.

High-brightness LED-phosphor coupling

Abstract: A high brightness LED phosphor coupling device. A semiconductor light source is encapsulated by a medium of first index of refraction, a layer of phosphor surrounded by a second medium of second index of refraction of optical index less than the first index and a light coupler for redirecting most of the light from the light source to an area of the phosphor about equal to the area of the light source multiplied by the square of the ratio of the first to the second index of refraction.

X-ray nanoscale profiling of layer-by-layer assembled metal/organophosphonate films.

Abstract: The nanoscale structure of multilayer metal/phosphonate thin films prepared via a layer-by-layer assembly process was studied using specular X-ray reflectivity (XRR), X-ray fluorescence (XRF), and long-period X-ray standing wave (XSW) analysis. After the SiO2 X-ray mirror surfaces were functionalized with a monolayer film terminated with phosphonate groups, the organic multilayer films were assembled by alternating immersions in (a) aqueous solutions containing Zr4+, Hf4+, or Y3+ cations and then (b) organic solvent solutions of PO3−R−PO3, where R was a porphyrin or porphyrin-square spacer molecule. The different heavy metal cations provided X-ray fluorescence marker layers at different heights within the different multilayer assemblies. The XSW measurements used a 22 nm period Si/Mo multilayer mirror. The long-period XSW generated by the zeroth-order (total external reflection) through fourth-order Bragg diffraction conditions made it possible to examine the Fourier transforms of the fluorescent atom dis...

Coherent grazing exit x-ray scattering geometry for probing the structure of thin films

Abstract: We demonstrate a diffraction geometry which provides strong sensitivity to the microstructure of thin films. While a coherent beam of x rays is being reflected from the surface of the sample, measurements were made of the scattering of the exit beam below the critical angle for total external reflection. This results in a strong signal with speckle modulations that are characteristic of the internal arrangement of grains at different depths within the film.

Effect of magnetic field of light on refractive index

Abstract: Light refraction in a medium results from energy exchange between the medium and the magnetic field of the light. Formulas of refractive index, that is, the ratio of light speed in vacuum to light speed in the medium, were derived with the inductor model of electron cloud and the law of energy conservation. Refractive indices of several media were calculated using the formulas derived and the calculated results are in agreement with the results measured. The anisotropy and the nonlinearity of the refractive index are explained with the theory described in this work.

Determination of Layer Thicknesses of Single Layers and Multilayers

Abstract: The measurement of layer thickness is a basic problem, and can be solved both by x-ray reflection and x-ray diffraction (see [121] for a review). In both methods, the thickness of a thin layer can be determined from the angular positions of the subsidiary maxima on the reflection (or diffraction) curves.

A setup for studies of ultra-small angle scattering of hard γ-quanta

Abstract: Based on the microtron MT-22C an experimental setup for the study of ultra-small angle scattering of up to 13 MeV γ-rays from macroscopically smooth surface has been constructed. Preliminary results for angular distributions and γ-spectra are presented.

Dual-wavelength x-ray monochromator

Abstract: A method for testing a surface includes finding respective first and second critical angles for total external reflection of radiation from an area of the surface at first and second wavelengths. The first and second critical angles are compared to determine an orientation of a tangent to the surface in the area.

High reflectivity and high flux x-ray optic element and method of making same using atomic layer deposition techniques

Abstract: This invention relates to a method of forming multiple bilayers on a substra te using an atomic layer deposition process. The reflecting layer of the bilaye r pair can be a high electron density metal and the spacing layer of the bilay er pair can be a low electron density material. Because atomic layer deposition can deposit atomic layer controlled and conformal films, multiple bilayers c an be deposited on the internal surfaces of monocapillary tubes. By applying a graded multiple bilayer, much higher reflectivity and higher flux optical elements can be obtained than those based on total external reflection. Deposition of a graded multiple bilayer on an elliptic or parabolic tapered tube leads to focused or collimated output from a point source input. Variou s atomic, layer deposition techniques are described to produce the graded multiple bilayer high quality X-ray focusing devices, especially for "hard" X- ~rays.

Colour image forming apparatus, which controls the image density by evaluating a reflection signal and a diffuse reflection signal of an optical detecting unit

Abstract: An amount of toner transfer on a reference pattern is calculated by using an optical detecting unit (130) that detects both regular reflection light and diffuse reflection light from a detection target simultaneously, based on a relative ratio between a value obtained by subtracting a result of multiplying a "diffuse reflection output" by a "minimum value of a ratio between a regular reflection output and the diffuse reflection output" from the "regular reflection output" of the density detection reference pattern, and a value obtained by subtracting a result of multiplying the "diffuse reflection output" by a "minimum value of a ratio between the regular reflection output and the diffuse reflection output" from the "regular reflection output" in the background of a transfer belt (120) or an intermediate transfer body (22).

Optical Detection of Motion of an Object with a Refractive Index Coinciding with the Refractive Index of the Surroundings

Abstract: Estimates of characteristics of light reflection from an object moving with a constant velocity in a medium whose refractive index coincides with the refractive index of the object are presented. The back-reflected radiation has a frequency shift owing to the Doppler effect, and the reflectivity turns out to be a quantity of the first order in the ratio of the velocity of motion to the velocity of light in a vacuum. If the velocity of motion of the surroundings near the object boundary varies in a boundary layer of a width that appreciably exceeds the wavelength, the reflectivity falls off exponentially with the ratio of these quantities. The estimates performed testify that the possibility of observing the effect of relativistic reflection under consideration is quite realistic.

Dynamical Scattering Effects at Grazing Incidence Conditions

Abstract: In the previous chapter, X-ray diffuse scattering from free-standing nanoscale islands was simulated exclusively by using the simple kinematical theory. The corresponding experiments were carried out at large angles of incidence \(\alpha_i\) compared with the critical angle of total external reflection so that refraction effects and the influence of the specularly reflected wave could be neglected. However, for grazing-incidence/exit scattering geometries such as GISAXS and GID these dynamical effects have to be taken into account, and the simulations have to be performed in the framework of the distorted-wave Born approximation. In order to visualize these dynamical effects, the model system of LPE-grown SiGe islands described in Chap. was again chosen. These islands are especially suitable, owing to their high perfection regarding uniform shape and size. Moreover, they are large enough to give a sufficiently high scattering signal. This enables us to qualitatively and quantitatively check the validity of the DWBA approach.

Waveguiding light in air with ultralow index metamaterials

Abstract: Metamaterials can be engineered to have the real part of the effective refractive index less than unity at optical wavelengths. These composite materials exhibit total external reflection and hence can be utilized in the cladding of hollow optical waveguides. We investigate the use of one- and two-dimensional silver-dielectric metamaterials in waveguides. In particular, we discuss the effects of scaling down the size of the metal features in the metamaterial.

Monitoring particle adsorption and thin film formation by laser reflectometry near the critical angle

Abstract: Reflection and transmission of the light in a random medium are composed by coherent and incoherent waves. The coherent one can be modeled as interacting with a medium with effective optical coefficients. In a random dilute suspension, the coherent wave travels in a medium with an effective index of refraction given by the van de Hulst formula. This effective index is, in general, complex. The imaginary part takes into account the loss of the coherent wave due to scattering. Internal reflection, due to random particles in suspension defines a critical angle determined by the effective index of refraction of the particles in suspension. The curve of reflectivity is smoothed near the critical angle by the imaginary part of the effective index of refraction. One can show that the diffuse component of the reflection tends to zero at the critical angle. In this work, laser reflectometry near the critical angle is used to study particle adsorption on a flat surface. We monitored the adsorption of polystyrene particles with positive and negative charge in suspension. This method allows the direct measuring of reflectivity and its angle derivative on the prism surface where is formed the film.

Refraction of a three-dimensional beam in uniaxial crystal-isotropic medium interfaces in presence of inhibited reflection

Abstract: We propose a generalization of Artmann's method for three-dimensional beams. This generalization, that does not consider a symmetry coordinate for the incident beam, allows its use in non-isotropic interfaces. We apply it particularly to the study of the refraction of a beam that is limited in two directions and that impinges on a uniaxial crystal-isotropic medium interface in presence of inhibited reflection. As known, the direction of the energy flux of a three-dimensional incident beam can be obtained (to first order and considering paraxial approximation) from the interference patterns of two two-dimensional beams. Each beam can be obtained from the superposition of two plane waves. In the first beam, the normals to the wave fronts are contained in the same incidence plane and they impinge with different angles; in the second, they are contained in different planes of incidence but with the same angle. We show that the refracted ray, in presence of inhibited reflection, suffers a lateral displacement that is not contained in the plane of incidence. The refraction of the first two-dimensional wave packet takes into account the longitudinal displacement whereas the refraction of the second allows us to calculate the transversal displacement.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Total reflection and inhibited reflection in a crystal-crystal interface: extraordinary incident wave

Abstract: In this article we consider an extraordinary monochromatic wave incident on an interface formed by two uniaxial crystals. We show a detailed analysis of the variation of the inhibited reflection and total reflection angles in terms of the refraction indices and the directions of the optical axes.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Application of total reflection mirrors for radiation gathering improvement of x-ray planar waveguide-resonator

Abstract: Planar X-ray waveguide-resonators (PXWR) possess by a spectrum of specific peculiarities forced to regard it as the base devices for X-ray nanophotonics [1]. But at all own attractiveness the simplest design PXWR is characterized by low total intensity of an emergent beam evaluated as some percentage of the beam intensity formed by slit-cut systems or polycapillary optics facilities. PXWR emergent beam low intensity is consequence of it’ s input aperture narrowness which is smaller as the conventional X-ray source focus projection on 3-4 orders. Owing to the aperture narrowness PXWR is able to swallow a little X-ray portion of the total source radiation flux correlated with the waveguide-resonator capture angle, only. (The capture angle can not exceed the double critical angle of total external reflection for PXWR reflector’ s materials.) So, the maximum intensity magnitude of PXWR emergent beam is objective limited by some value at the immutable source power. But this value can be enhanced in result of the special modifications. Our investigation showed that the similar modification can be executed by using of two addition planar total reflection mirrors disposed near PXWR inlet. Right disposition of the mirrors allows to turn an additional portion of initial source flux into the angular capture gate of PXWR. Measurements carried out for different space dispositions of the mirrors demonstrated that the mirror’ s arrangement led to maximum profit for all PXWRs emergent beam parameters is not existed. It is possible to expect that the problem of disposition ambiguity is connected with the necessity to use nonplanar mirrors. At the same time, the mirrors application allowed to achieve increasing of the total intensity for the characteristic component of PXWR emergent beam approximately on 3 times. In all cases of the mirrors using the divergence of PXWR emergent beam reached own highest level been equal to the double magnitude of PXWR reflectors material total reflection critical angle. The space radiation distribution of the characteristical Xray component in emergent beam was depended from the mirrors disposition. We believe that the ways search for the waveguide-resonator properties improving is the important task of X-ray nanophotonics. And the modernization of X-ray beam formers functioned on base of PXWR by application of total reflection radiation concentrators is the beautiful way for an efficiency enhancing of X-ray procedures oriented on the waveguideresonance devices utilization.

New principles of diagnostics of surface parameters of solids by methods of x-ray total external reflection

Abstract: The series of GaAs and SiO2 samples with the specially prepared one- and two-dimensional surface reliefs have been investigated by the methods of integral and differential curve of X-ray total external reflection. The direct and inverse problems were solved, taking into consideration data obtained by the method of atomic-force microscopy. The theoretical curves of total external reflection are calculated and the parameters describing a surface relief of the samples are restored. The fractal approach for describing of the shape of differential curves and surface profiles was used.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Quantifying the thickness of magnetically active layers using x-ray resonant magnetic scattering

Abstract: X-ray resonant magnetic scattering measurements below and above the critical angle for total external reflection allow fitting to extract the magnetically active volume within specific magnetic layers Uncapped ultrathin Co films deposited onto Ni on Si display more magnetic resonant response than do those grown directly onto the native oxide of Si