scholarly journals SPECTRAL AND ANGULAR DEPENDENCE OF THE EFFICIENCY OF A TWO-LAYER AND SINGLE-RELIEF SAWTOOTH MICROSTRUCTURE

2018 ◽  
Vol 42 (1) ◽  
pp. 38-43 ◽  
Author(s):  
G. I. Greisukh ◽  
V. A. Danilov ◽  
A. I. Antonov ◽  
S. A. Stepanov ◽  
B. A. Usievich
Keyword(s):  
Angular Dependence ◽  
Diffraction Efficiency ◽  
Optical Glass ◽  
Angle Of Incidence ◽  
Precision Casting ◽  
Optical Plastics

Spectral and angular dependences of the diffraction efficiency of two-layer single-relief sawtooth microstructures are analyzed. The microstructures are assembled from optical plastics and new brands of special optical glass. This makes it easy to replicate elements with diffraction microrelief by precision casting or stamping. Wide possibilities of weakening the dependence of the diffraction efficiency of such microstructures on the wavelength and the angle of incidence of radiation on the element are demonstrated.

scholarly journals Polarimetry of anisotropic surface layer on glass

2020 ◽  
pp. 95-98
Author(s):  
A. L. Yampolskiy ◽  
O. V. Makarenko
Keyword(s):  
Surface Layer ◽  
Total Internal Reflection ◽  
Optical Glass ◽  
Subsurface Layer ◽  
Polarization Degree ◽  
Angle Of Incidence ◽  
Weak Anisotropy ◽  
Near Surface ◽  
Anisotropic Surface ◽  
Higher Order Modes

Investigating the Stokes vector of light reflected from the surface of the optical glass, the presence of an anisotropic surface layer was established. The phase difference between radiation p- and s-components is revealed, which varies depending on the angle of incidence. This shows a weak anisotropy. Assuming that the anisotropic layer has an increased refractive index due to its chemical-mechanical treatment, it can be considered as some near-surface weakly guiding gradient burried waveguide. The possibility of coming radiation into such a planar waveguide using a coupling total reflection prism was investigated. The inspection showed a violation of the total internal reflection, unequal for p- and s-polarizations, which confirms the presence of the subsurface layer and its anisotropy. The absorption of radiation, which could be compared with the excitation of modes, is small. This is due to the properties of the prism material. Also, higher order modes are absorbed better. There is no significant angular dependence of the polarization degree of the output beam; however, it is higher in the case of s-polarization.

ANGULAR DIFFERENTIAL DOSE ALBEDO MEASUREMENTS FOR 0.66-Mev γ's INCIDENT ON CONCRETE, IRON, AND LEAD

1964 ◽  
Vol 42 (5) ◽  
pp. 957-971 ◽  
Author(s):  
C. E. Clifford
Keyword(s):  
Monte Carlo ◽  
Angular Distribution ◽  
Angular Dependence ◽  
Normal Incidence ◽  
Angular Distributions ◽  
Angle Of Incidence ◽  
Monte Carlo Program ◽  
Shadow Zone

The angular dependence of the scattered dose produced by 0.66-Mev γ's incident on concrete, iron, and lead was measured for angles of incidence of 0°, 30°, and 60°. The angular distributions from these materials were dependent both on the angle of incidence and on the angle of scatter to a detector and could not be related to each other by simple multiplicative factors. As the angle of incidence increased, the scattering in the forward directions became increasingly anisotropic for each material. For iron exposed at normal incidence the effect of the scatterer thickness on the angular distribution of the scattered dose was measured also.A Monte Carlo program was used to study the distribution of distances between the point of incidence and the point at which a backscattered γ emerged and indicated that scatter from the "shadow" zone could be significant in some shielding studies. The program was used also to study the distribution of depths of the point at which a backscattered γ had its last scattering interaction.

Study on the Fabrication of Blazed Grating with Sub-Micrometer Space on Aluminum Film

2006 ◽  
Vol 532-533 ◽  
pp. 397-400
Author(s):  
Shi Lun ◽  
De Fu Hao ◽  
Xiang Dong Qi
Keyword(s):  
Diffraction Efficiency ◽  
Diamond Tool ◽  
Optical Glass ◽  
Aluminum Film ◽  
Zero Order ◽  
Blazed Grating ◽  
Positioning Control ◽  
The Real ◽  
Grating Interferometer ◽  
Grating Diffraction

The saw tooth grooves of blazed grating ruled by ruling engine are formed by diamond tool which presses on the aluminum film evaporated on the substrate of optical glass or metal. The real shape of ruled saw tooth groove is different from that of the ideal groove and the ruling process indicates that there are the zero order planes, similar to the flat tops, on the grating grooves. The results of Fourier analysis for the real ruled grating featuring the zero order plane structure shows that the flat top width is an important factor for grating efficiency. Additionally, bigger pressure value loaded on the diamond tool and bigger lateral pressure value on the aluminum film will be benefit to the improvement of grating diffraction efficiency. Based on the grating interferometer, the high precision positioning control system of ruling engine guarantees the accuracy of the grooves space. High density blazed grating whose space is 0.83μm is manufactured and its’ grooves spaces are very equidistant and uniform under the view field of AFM. And the infrared blazed grating, whose diffraction efficiency in the first order is up to 97 percent, is ruled successfully also.

Determination of the Percentage of the Cubic and Hexagonal Phases in Gan with Nexafs

1996 ◽  
Vol 449 ◽  
Author(s):  
M. Katsikini ◽  
E. C. Paloura ◽  
T. D. Moustakas ◽  
E. Holub-Krappe ◽  
J. Antonopoulos
Keyword(s):  
Angular Dependence ◽  
Mixed Phase ◽  
Angle Of Incidence ◽  
X Ray ◽  
Surface Normal ◽  
Cubic Gan ◽  
Phase Sample ◽  
X Ray Absorption ◽  
Absorption Measurements

ABSTRACTAngle resolved near edge X-ray absorption measurements (NEXAFS) are used to access the existence and concentration of the two allotropic phases, cubic (β-GaN) and hexagonal (α-GaN), that coexist in a mixed-phase GaN sample grown by ECR-MBE. The resonance intensities in the NEXAFS spectra from a pure cubic GaN sample are independent of the angle of incidence ϑ, while they have a characteristic angular dependence on cos2ϑ for the hexagonal material, i.e. I=A±Bcos2ϑ. From the values of A and B the bond orientations with respect to the surface normal are calculated. Furthermore, the NEXAFS resonances in a pure α- or β-GaN sample appear at characteristic energies which are independent of the angle of incidence ϑ. Contrary to that the NEXAFS resonances in the spectra from a mixed-phase GaN show a characteristic ϑ-dependent shift. On the basis of this finding, a method is proposed and applied for the determination of the fractions of the co-existing polytypes in a mixed-phase sample.

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

Electron-Channelling Patterns: Principles and Techniques

1976 ◽  
Vol 34 ◽  
pp. 400-401
Author(s):  
David C. Joy
Keyword(s):  
Crystal Structure ◽  
Electron Flux ◽  
Lattice Structure ◽  
Incident Beam ◽  
Bloch Wave ◽  
Crystalline Solid ◽  
Angle Of Incidence ◽  
Electron Channelling ◽  
Regular Arrangement ◽  
Backscattered Signals

In a crystalline solid the regular arrangement of the lattice structure influences the interaction of the incident beam with the specimen, leading to changes in both the transmitted and backscattered signals when the angle of incidence of the beam to the specimen is changed. For the simplest case the electron flux inside the specimen can be visualized as the sum of two, standing wave distributions of electrons (Fig. 1). Bloch wave 1 is concentrated mainly between the atom rows and so only interacts weakly with them. It is therefore transmitted well and backscattered weakly. Bloch wave 2 is concentrated on the line of atom centers and is therefore transmitted poorly and backscattered strongly. The ratio of the excitation of wave 1 to wave 2 varies with the angle between the incident beam and the crystal structure.

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

On resolving fine periodic microstructures in the optical microscope

1989 ◽  
Vol 47 ◽  
pp. 364-365
Author(s):  
W.S. Putnam ◽  
C. Viney
Keyword(s):  
Liquid Crystalline ◽  
Numerical Aperture ◽  
Polarized Light ◽  
Normal Incidence ◽  
Optical Microscope ◽  
Angle Of Incidence ◽  
Resolution Limit ◽  
Crystalline Materials ◽  
Periodic Microstructures ◽  
Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

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