Showing papers on "Total external reflection published in 1986"

Device for modulating and reflecting electromagnetic radiation employing electro-optic layer having a variable index of refraction

Abstract: A multi-layer device for modulating and reflecting light. The device is formed of an electro-optic layer with a variable index of refraction sandwiched between two other layers having a pre-determined index of refraction. An electric field applied across the electro-optic layer controls the index of refraction of the layer and thus the reflectance and transmittance of light through the multi-layer stack. The device can therefore be used as a mirror, window, beam-splitter, shutter, light modulator, or other optical logic element.

Novel x-ray diffractometer for liquid surface studies

Abstract: An x‐ray diffractometer for studying the structure of the liquid–vapor interface is described. It is designed to permit reflectivity and scattering studies from liquid surfaces for angles varying from grazing incidence, below the critical angle for total external reflection up to angles ∼3° using a rotating anode x‐ray generator. In principle the diffractometer system can be used to study both the density profile normal to the surface and in‐plane structural features. The former is determined by deviations of the measured reflectivity from the Fresnel law of classical optics and the latter from nonspecular scattering. Results obtained using this spectrometer to measure the density profile normal to the surface of water and a liquid crystal are presented.

Reflection of light by a random layered system

Abstract: We consider the transmission and reflection of light by a layered medium where the optical index of every layer is a constant which fluctuates from one layer to another. In the limit of a very large number N of layers, the transmission coefficient vanishes exponentially, and the medium becomes an ideal reflector. A new simple method is used to evaluate the penetration depth ξ for normal incidence and at the critical angle for total reflection of the homogeneous equivalent medium. For a Gaussian distribution with width ζ of the fluctuating part of the index, we find ξ∼ζ −2 and ξ c ∼ζ −2/3 , respectively. We also discuss the properties of the reflection coefficient and show computer simulations. We expect our results to be also valid for neutron transmission Evaluation de la longueur de penetration a l'incidence normale et pour l'angle critique de reflexion totale du milieu homogene equivalent

Methods for reducing the fresnel reflection in an optical-fiber connector with index matching material.

Abstract: If there is a discontinuity of the refractive index in optical fibers connected with an optical connector, the light is reflected from this part to the light source, creating a problem in its light transmission characteristic. The main causes of the discontinuity are: (1) the gap between the endfaces of the optical fibers; and (2) the change of the refractive index at the end-face of the fibers due to their polishing. Solutions to these problems are investigated in this paper, using silica-based graded index multimode optical fibers. For (l), a refractive-index matching material is employed, and the method for selecting the central value of the refractive index and the temperature coefficient from the reflected light in the visual-light wavelength region is investigated. It has been confirmed that the refractive-index matching material made of silicone resin and chosen by this method can obtain the required reflection loss greater than 40 dB, in each of the transmission wavelengths of 0.85 pm and 1.3 μm, and in the temperature range of −30°C to +60°C. For (2), the relationship between the polishing conditions and the reflected light power was investigated. It has been found that the refractive index of the endface of an optical fiber changes slightly when polished. The conditions of polishing for suppressing this change have been determined, and the property of the polished endface has been clarified.

Fabry-perot spectroscope

Abstract: PURPOSE: To facilitate the obtaining of a high wavelength resolving power, without combined use of additional spectroscope or the like, by making the surface opposite to a reflection film surface of one of two transparent plates non-parallel with the reflection film surface while a reflection film is applied at a part thereof. CONSTITUTION: To make a luminous flux 7 incident into reflection film surfaces 3 and 4 of a Fabry-Perot interference plate in such a manner as to differentiate the angle of refraction at least twice, a surface 6 opposite to the reflection film surface 4 of the transparent plate 2 is arranged at a specified angle so as to be non-parallel with the reflection film surface 4 while a reflection film is applied on the surface 6 to make a reflecting surface. Moreover, a voltage is applied properly to a piezo-electric element 5 to control the interval between the two transparent plates 1 and 2. Then, the luminous flux 7 is made incident into the Fabry-Perot interference plate comprising the reflection film surfaces 3 and 4 arranged at an interval (h) to give θ1' in the angle of refraction while the transmission light is reflected with the surface 6 to be incident into the Fabry-Perot interference plate to give θ2' in the angle of refraction. Thus, adjacent wavelengths are removed thereby enabling the extraction of the luminous flux as transmission light 7' having a specified wavelength only. COPYRIGHT: (C)1988,JPO&Japio

The Characterization of Cryogenic Materials by X-Ray Absorption Methods

Abstract: X-ray absorption techniques have in recent years been developed into powerful probes of the electronic and structural properties of materials difficult to study by other techniques In particular, the extended x-ray absorption fine structure (EXAFS) technique can be applied to a variety of cryogenic materials Three examples will be used to demonstrate the power of the technique The first is the determination of the lattice location of dilute alloying additions such as Ta and Zr in Nb3Sn The Ta additions are shown to reside predominately in Nb lattice sites, while Zr is not uniquely located at either Nb or Sn sites In addition to structural information, temperature dependent EXAFS studies can be used to determine the rms deviations of atomic bond lengths, providing information about the temperature dependence of interatomic force constants For Nb3Sn deviations are found from simple harmonic behavior at low temperatures which indicate a softening of the Nb-Sn bond strength The final example is the study of interfacial properties in thin film systems This is accomplished by making x-ray absorption measurements under conditions of total external reflection of the incident x-rays As some examples will show this technique has great potential for studying interfacial reactions, a process used in the fabrication of many superconducting materials

Experimental Determination of Electron Escape Weight Functions by Using the Methods of ``Calibrated Amorphous Layers'' and ``Total External Reflection''

Abstract: The electron escape functions for various final energies of electrons are measured under the conditions of interaction of characteristic CuKα radiation with a germanium specimen. The energy analysis is carried out by a proportional gas counter of electrons with energy resolution ≈ 18%. The measurements are carried out by using two independent techniques: the method of „calibrated amorphous layers” and the new method of „total external reflection”. The features of the second method are: the universality with respect to the specimen structure (the method can be applied to single-crystalline, polycrystalline, and amorphous samples) and the high speed of measurements. [Russian Text Ignored].

Reflective Optics for Soft X Rays I Grazing Incidence

Abstract: As discussed in Chapter 1, the reflectivities of single surfaces at normal or near-normal incidence for soft X rays are very small. High reflectivities from single surfaces are only obtained at grazing angles of incidence. This is because the refractive index of the reflecting medium is very close to, and slightly less than, that of the surrounding medium (vacuum)—the conditions under which total external reflection can occur.

Interface exafs using glancing angles

Abstract: The use of glancing angles t o o btain EXAFS signals from thin interfacial regions is described. The technique is applicable t o the case of a light overlayer on a heavy substrate for which total external reflection can be caused to occur at the interface. In t his case the p enetration into the substrate is very small (520-30 A in many cases). Data have been obtained on two systems: A1 on Cu and Ag on Au. The A1 on Cu samples had 1000 A of A1 on Cu and measurements were made on the interface structure as a function of annealing temperature. For anneals above 140°C clear indication of the growth of CuAIZ at the interface is observed. The interface sensitivity was then verified by varying the glancing angle to determine the CuA12 layer thickness. Even for CuA12 layers as thin as 100 A, the EXAFS signal is essentially pure CuAl2 with little contamination from the underlying Cu. For Ag on Au there is no compound formation and these techniques were used to look at interdiffusion as a function of annealing. In particular the Au environment in Ag grain boundaries could be detected. Understanding the structure of solid state interfaces is important for studies of solid state reactions, t hin film adhesion and stability. Traditional probes such as Auger sputter p rofiling and Rutherford backscattering can provide compositional information but no detailed structural information, and for buried interfaces often have only limited depth resolution. For single crystal interfaces electron microscopy can provide beautiful images, but sample preparation can be tedious and many systems involve polycrystalline or amorphous interfaces. In this paper the applications of glancing angle x-rays to the study of buried interfaces are discussed with particular emphasis on interface extended x-ray absorption fine s tructure (ExAFS) measurements.