Showing papers on "Total external reflection published in 1999"

Grazing incidence small angle x-ray scattering from free-standing nanostructures

Abstract: We develop the theory for grazing incidence small-angle x-ray scattering (GISAXS) from nanometer-sized naked islands on a flat substrate in the framework of the distorted-wave Born approximation (DWBA). The scattered wave amplitude is composed of four terms, including all combinations of scattering from the islands and reflection from the substrate. We apply this theory to x-ray measurements on Ge islands grown on Si(111), and show that we can determine the full triangular symmetry of these islands. The results also show that the DWBA must be used for smooth substrates near the angle of total external reflection. We finally discuss the advantages of GISAXS as compared to transmission small angle x-ray scattering for determining the symmetry of nanostructures.

Polycapillary X-ray optics for microdiffraction

Abstract: Polycapillary optics, i.e. shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, can be used to redirect, collimate or focus X-ray beams. X-rays emitted over a large angular range from conventional laboratory-based sources can be transformed into a beam with a small angular divergence or focused onto a small sample or sample area. Convergent beams of X-rays, with convergence angles as high as 15°, have been produced using polycapillary X-ray optics. Focused-spot sizes as small as 20 µm have been achieved, with flux densities two orders of magnitude larger than that produced by pinhole collimation. This results in a comparable decrease in data collection times because of the increase in direct-beam intensity and reciprocal-space coverage. In addition, the optics can be employed to reduce background and provide more convenient alignment geometries. The inverse dependence of the critical angle for total external reflection on photon energy results in suppression of high-energy photons. This effect can be employed to allow the use of higher tube potentials to increase the characteristic line emission and has also been employed to increase significantly the Kα/Kβ ratio in Cu radiation. Measurements of X-ray diffraction data and crystallographic analyses have been performed for systems ranging from elemental crystals to proteins. Data from a lysozyme protein `standard' with a slightly convergent beam, taken in 3 min per frame with 2° oscillation with a 2.8 kW source, refined to an intensity variance of 5% compared to a standard data set. High-quality data were also obtained with a 0.03 kW fixed-anode source and a 2° convergent lens in 5 min per frame.

Rugate filter and method of making same

Abstract: A rugate filter coating for reflecting at least a portion of at least one electromagnetic wavelength band, the filter comprising a transparent coating on a substrate, the coating having an incrementally varying refractive index of refraction depth, with each of the increments having a constant a constant index of refraction. The index of refraction of the increments determined by calculating the index of refraction profile of the coating, dividing the continuous index of refraction coating into increments and setting the constant of refraction for each of the increments equal to the average index of refraction of the continuous index of refraction over the increment.

Roughness Correlation and Interdiffusion in Thin Films of Polymer Chains

Abstract: The surface morphology of thin bilayer polymer films on top of glass substrates was investigated. The bilayer consists of a blend film of protonated and deuterated polystyrene and an underlying deuterated polystyrene film. Choosing the thickness of the top film larger than 8 times and smaller than 2 times the radius of gyration of the chains enables the determination of film thickness and confinement effects. With diffuse neutron scattering at grazing incidence in the region of total external reflection, a depth sensitivity and a contrast even at the internal polymer-polymer interface was achieved. The underlying film is conformal to the substrate, and depending on the thickness of the top film two different types of roughness correlations are observed. Thin confined films nestle to the underlying polymer films, while the stiffness of thicker bulky films provides an independent morphology. In both cases, annealing above the glass-transition temperature yields an interdiffusion at the internal polymer-polymer interface, and the polymer-air surface remains essentially unchanged with respect to roughness correlations.

Differential reflection phase shift under conditions of attenuated internal reflection

Abstract: The angle-of-incidence dependence of the differential reflection phase shift Δ between p and s polarizations is considered a function of the real and imaginary parts of the relative complex dielectric function e of an interface in the domain of fractional optical constants, i.e., under conditions of internal reflection. The constraint on complex e such that oscillatory and monotonic angular responses are obtained is determined. A sensitive and stable technique, which is based on attenuated internal reflection ellipsometry between the Brewster angle and the critical angle, is proposed for measuring small induced absorption (ei∼10-5) in the medium of refraction.

Structural characterization of a lamellar W/Si multilayer grating

Abstract: A lamellar multilayer grating of the nominal normal and lateral periods 8 and 800 nm, respectively, was obtained by etching a planar amorphous W/Si multilayer up to the substrate. The specular reflectivity, grating truncation rods of nonzero orders, and a reciprocal space map of the scattered intensity close to the total external reflection were measured using the Cu Kα radiation. We demonstrate an extraction of real structural parameters of a fully etched periodic multilayer grating from fitting the measured truncation rods based on the matrix modal eigenvalue approach to the dynamical theory of reflectivity by gratings.

Synchrotron radiation glancing incidence X-ray diffraction: a tool for structural investigations of ion implanted glasses

Abstract: The availability of very intense and highly collimated synchrotron radiation beams coupled with the glancing incidence geometry makes possible to study ion implanted glasses with X-ray diffraction. We maximize the contribution to the scattering of the metal-rich (clusters) layer by working at the critical angle for total external reflection at the implanted layer-substrate interface. By using the refracted beam as a probe the diffraction profile of the metallic clusters in very diluted samples (a single implant in the 10 16 at/cm 2 range) can be extracted. We report some results on SiO 2 glasses implanted with Cu and Ni. We used a very intense monochromatic 10(h) × 24(v) μm 2 beam from an undulator source. The data were collected by using an imaging plate (IP) system with integration times in the order of minutes. From the azimuthal integration of the images the clusters diffraction pattern can be extracted enabling crystalline phases identification, the retrieval of the lattice parameters and in some cases the determination of the clusters sizes.

Grazing-incidence X-ray diffraction in the study of metallic clusters buried in glass obtained by ion implantation

Abstract: A novel X-ray technique is described for carrying out structural investigations of metallic nanoparticles buried in glass obtained by ion implantation. The method consists of maximizing the scattering contribution of the cluster-rich layer by working at the critical angle for total external reflection at the implanted-layer–substrate interface. By using the refracted beam as a probe, the diffraction profile of the metallic clusters in very dilute samples can be extracted by a simple subtraction procedure. The new procedure is applied to SiO2 glasses implanted with Ag ions. The study was performed at the European Synchrotron Radiation Facility. The results indicate that a complete structural investigation can be performed by using highly collimated, very intense synchrotron radiation beams, a grazing-incidence geometry and two-dimensional detectors. The procedure is shown to be very useful for complementing the information from electron techniques (transmission electron microscopy, micro-beam electron diffraction) and X-ray spectroscopic (EXAFS) methods. In particular, the accuracy of the lattice-parameter determination is shown to be a factor of nine better than the accuracy of EXAFS results.

Optical phase change on reflection at v-SiO2/Sn interface

Abstract: An interferometric method was used for determination of the phase change on reflection at v-SiO 2 /Sn interface in the infrared wavelength range in terms of IR spectroscopy. By evaluating the maximum (or minimum) positions of the interference fringes produced by multiple internal reflections at air/v-SiO 2 /air and air/v-SiO 2 /Sn interfaces, the wavelength-dependent refractive index of vitreous silica and phase change on reflection at v-SiO 2 /Sn interface were determined. The evaluated refractive index of vitreous silica can be described with a three-term Sellmeier equation. The phase change on reflection was found to decrease with increasing wavelength of the incident light.

Frustrated total internal reflection evanescent switching

Abstract: The mechanism of frustrated total internal reflection was analyzed according to the theory of optical film. The transmission and reflection functions were developed and the curves of transmission and reflection changing from the relative gap width d / λ , incident angle θ 0 , and refraction index n were shown in graphs. We proposed a scheme of experimental device to test the theoretical conclusion. A self-made electronic actuator drove the piezoelectric ceramics of FTIR. Experiments showed that the evanescent of transmission is 80% for He–Ne laser and smaller for YAG laser and Er:glass laser.

Diffraction geometry optimization with polycapillary x-ray optics

Abstract: Polycapillary optics, shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, can be used to redirect, collimate, or focus x-ray and low energy neutron beams X rays emitted over a large angular range from conventional, laboratory-based sources can be transformed into a beam with a small angular divergence or focused onto a small sample or sample area Focused spot sizes as small as 20 micrometer have been achieved, with flux densities more than two orders of magnitude larger than that produced by pinhole collimation This results in a comparable decrease in data collection times due to the increase in direct beam intensity and reciprocal space coverage In addition, the optics can be employed to reduce background and provide more convenient alignment geometries The inverse dependence of the critical angle for total external reflection on photon energy results in suppression of high energy photons This effect can be employed to allow the use of higher tube potentials to increase characteristic line emission Using parallel beam geometries peak shapes are found to be symmetric and independent of angle and sample alignment Measurements of x- ray diffraction data and crystallographic analysis have been assessed for powders, thin films, minerals, elemental crystals, polymers, and protein crystalsThe benefits and limitations of polycapillary optics for such measurements will be reviewed

On the “supercollimation” of X-ray beams in rough interfacial channels

Abstract: The transmission of x rays through rough submicron narrow channels is investigated by numerical simulation with diffraction and decay of coherence taken into account. It is found that transmission is strongly increased for directions within the diffraction limit λ/d (d is the channel width). For larger angles strong roughness scattering results in rapid decay of coherence and absorption of the x-ray beams. When the coherent part is a significant portion of the transmitted beam, its divergence is also within the diffraction limit, which can be an order of magnitude smaller than the Fresnel angle of total external reflection. The effects are explained with the statistical theory of x-ray scattering in a rough transitional layer. Such “supercollimation” can be used for fine angular discrimination of x radiation and for the production of very narrow diffraction-quality x-ray beams.

Behavior of total internal reflection in optical crystals

Abstract: It is shown that a crystal can be cut so that one incident beam undergoing reflected from an inclined face inside the crystal excites four beams, two ordinary and two extraordinary, propagating in different directions.

Total internal reflection of a Gaussian light beam

Abstract: An approximate theoretical model for calculating the reflected and refracted fields of a Gaussian light beam at a plane interface between two isotropic media is formulated on the basis of a Fourier integral. In the vicinity of the critical angle of incidence (for total internal reflection) the model predicts the presence of two refracted beams, one displaced along the interface by an amount equal to the Goos-Hanchen shift; curvature of the phase fronts and nonalignment of the effective directions of energy and phase propagation occur for each beam, as in an anisotropic medium.

Optical refractive synchronization coherent information in a waveguide

Abstract: Fundamentally, the process of refraction is the change of energy, direction or speed of a light beam which is propagating through a medium. In the one case, the change in direction is a continuous bending of the light beam and the subsequent change of speed of the light beam which is propagating through a medium. In the one case, the change in direction is a continuous bending of the light beam and the subsequent change of speed of the light in the medium which is referred to as the index of refraction of the material. In the second case, there is the abrupt change in the index, polarity or phase of the medium which directs the energy out of the medium, or changes the ability of the light to pass through the medium, thereby absorbing the energy. The second case is the technique employed in Optical Refractive Synchronization. The light is passed through a crystal which has the refractive index changed abruptly, and subsequently the electric field, by mixing a radio frequency signal into the crystal which then creates a modulation on to the wavelength of light passing through, or absorbing, in the crystal at the frequency of the radio signal that is to be modulated onto the light beam. This Optical Modulation is performed, therefore, through the application of the refraction of the optical signal.

Just lower illumination device

Abstract: PROBLEM TO BE SOLVED: To assure the illumination of high luminance of a just lower illumination device and to assure the uniformity of this luminance to the extent visible to naked eyes. SOLUTION: The reflection surface 7 of a light source 5 comprises a reflection surface group 8 consisting of a first reflection part 8 which supplies the reflected light to a reflected light range B so as to make up the degradation in the luminance of a direct projection light range A of the light source 5, and a second reflection part 82 constituting a multiface reflection surface for supplying the reflected light to the reflected light range C and a build-up reflection surface 9 in the central position of the light source 5. The build-up reflection surface 9 is composed of an arcuate reflection surface 91 of a small diameter and an intermediate reflection surface 92 of a large diameter. The reflected light thereof is supplied in overlap to the reflection ranges B and C. As a result, the reflected light of the build-up reflection surface 9 is made into regulating light and the uniformity of the luminance is assured.

Correlation of Fresnel's interface reflection coefficients of external and internal reflection at the same angle of incidence for dielectric-dielectric interfaces

Abstract: The pair of Fresnel amplitude reflection coefficients for internal and external reflection, that apply when p- polarized light is incident on an interface between two transparent media form opposite sides at the same angle of incidence, are considered jointly and plotted together. This creates an interesting family of curves, with the angle of incidence as a parameter. Besides the well known characteristics of total reflection at the critical angle and total refraction at the Brewster angle, some unusual properties become apparent that pertain to light reflection at the special angles of 45 degrees and 51.827 degrees. The Stokes relations apply strictly at normal incidence, and approximately at other angles for nearly vanishing interfaces. The corresponding result for the Fresnel reflection coefficient for the s polarization, and for the ratio of p and s reflection coefficients, are also obtained.

New anomalous grazing X-ray reflection method for determining the atomic number density in multi-layered thin film

Abstract: A new method has been proposed for determining the atomic number density of a specific element in multi-layered thin films using grazing X-ray reflection and anomalous dispersion effect with the help of the Fourier filtering technique. The essential equations for analyzing the measured reflection data using the anomalous grazing X-ray reflectometry (AGXR) were given and the capability of this new method was demonstrated by obtaining the atomic number densities of constituents in a multi-layered thin film consisting of GaAs/AlAs/GaAs heterostructure.

Optical Measurement of a Refractive Index for Large Sphere via Scattering

Abstract: A simple method is demonstrated to determine the index of refraction of dielectric spheres by observing the scattering of visible light. Theoretical calculations show that there is an approximately linear relationship exists between the size parameter x=ka=2πn1a/λ of the scattering sphere and the number of maxima and minima in the scattered field as a function of angle when the size parameter in the 6000–12000-region.

Present Status and Future Prospects of Hard X-Ray Imaging Optical Systems

Abstract: The total external reflection of a single-layer mirror is no longer useful for grazing incidence optics in the hard x-ray region (10-100keV), whereas the Bragg reflection of multilayers is more advantageous in this region. Recently, a hard x-ray telescope was tested for practical use in the energy band 24-36 keV by making use of multilayer supermirrors. The focused image was measured by a newly developed position-sensitive CdZnTe solid-state detector. Further development of hard x-ray optical systems is proceeding in orderto extend the energy region up to 100keV and to improve the image resolution. These developments may open upnew research fields in the hard x-ray region.

Beam path divergence apparatus for laser projection display system

Abstract: The apparatus includes an inlet surface (101) which forms an anti reflection area which inlets light of a specific wavelength in a medium which has any refraction index without reflection. A first total reflection surface (105) is provided for the divergence of the beam path by an angle of the total reflection determined by the refraction index of the medium for the total reflection of the light which is inlet by the input surface. A second total reflection area (106) is formed for the divergence of the beam path by the angle of the total reflection for the total reflection of the light which is reflected by the first total reflection surface. N third total reflection surfaces are provided for the divergence of the beam path by the angle of the total reflection for generating a specific optical path by the total reflection of the light which is reflected by the second total reflection surface. An outlet surface forms an anti reflection surface and outlets the light which is reflected by the third total reflection surface.