Types Of Interference Patterns Research Articles

Formation of half-period surface relief gratings in azobenzene containing polymer films

We study the peculiar response of photo-sensitive polymer films irradiated with a certain type of interference pattern where one interfering beam is S-polarized, while the second one is P-polarized. The polymer film, although in a glassy state, deforms following the local polarization distribution of the incident light, and a surface relief grating (SRG) appears whose period is half the optical one. All other types of interference patterns result in the matching of both periods. The topographical response is triggered by the alignment of photo-responsive azobenzene containing polymer side chains orthogonal to the local electrical field, resulting in a bulk birefringence grating (BBG). We investigate the process of dual grating formation (SRG and BBG) in a polymer film utilizing a dedicated set-up that combines probe beam diffraction and atomic force microscopy (AFM) measurements, and permits acquiring in situ and in real-time information about changes in local topography and birefringence. We find that the SRG maxima appear at the positions of linearly polarized light (tilted by 45° relative to the grating vector), causing the formation of the half-period topography. This permits to inscribe symmetric and asymmetric topography gratings with sub-wavelength period, while changing only slightly the polarization of one of the interfering beams. We demonstrate an easy generation of sawtooth profiles (blazed gratings) with adjustable shape. With these results, we have taken a significant step in understanding the photo-induced deformation of azo-polymer films.

Binaural speech unmasking and interference in adult bilateral cochlear-implant users

Bilateral cochlear implants (BICIs) provide improved speech perception in noise, primarily derived from the head-shadow benefit. BICI listeners can also demonstrate binaural speech unmasking or squelch, particularly if the interferer is a single other speaker. However, under the same conditions, some BICI listeners can experience interference. This study tested 21 adult BICI listeners on speech understanding using a range of masker conditions (1, 2, 3, or 4 same-sex talkers, speech-modulated noise, or speech-shaped stationary noise). For listeners that showed binaural unmasking, the amount of unmasking was highest for the one-talker condition and least for the stationary noise, decreasing as the number of interfering talkers increased and the envelope modulation depth decreased. For listeners that showed interference, there were mainly two types of interference patterns: (1) where the amount of interference varied idiosyncratically across masker type, and (2) any stimulation in one ear essentially produced chance performance in the other ear for all masker conditions. The latter interference pattern occurred for the listeners with the largest asymmetries in speech understanding. This suggests, in these extreme cases, a possible central cortical processing bias for one ear and a more equal speech understanding between the ears may diminish interference.

Near-field properties of double nanoslits coupled with a wide collection cavity drilled on a metal film

Abstract The transmission and interference characteristics of light through slit-doublet structure milled in a metal film are significantly changed by introducing a wide collection cavity. We investigate them by the finite-difference time-domain method. Two types of interference patterns on the output surface, i.e., the periodic single peak or the periodic double peaks profile, are observed by varying the thickness of the double slits. It is also found that the peak value of the near-field interference fringes can be enhanced nearly two times that in normal slit-doublet structure (without the wide collection cavity). The physical mechanism is explained in detail.

Three types of bulk impurity induced interference patterns on the (100) and (111) faces of Ne- and Ar-doped silver

Scanning tunneling microscopy and $dI/dV$ mapping reveal three types of interference patterns on Ag(100) and Ag(111) after implantation of argon or neon. These patterns originate from the scattering of bulk electrons between subsurface impurities and the surface. Above nanocavities, the interference pattern develop a rich internal structure. Above point impurities, two types of simpler patterns develop that differ in corrugation, shape, and energy dependence. Low corrugated patterns show a strong dependence on energy, while more corrugated patterns hardly vary with energy. In addition, only the high corrugated patterns reflect the symmetry of the surfaces, while the low corrugated patterns are circular.

Tectonic setting of the Balaram-Kui-Surpagla-Kengora granulites of the South Delhi Terrane of the Aravalli Mobile Belt, NW India and its implication on correlation with the East African Orogen in the Gondwana assembly

Granulites are developed in various tectonic settings and during different geological periods, and have been used for continental correlation within supercontinent models. In this context the Balaram-Kui-Surpagla-Kengora granulites of the South Delhi Terrane of the Aravalli Mobile Belt of northwestern India are significant. The granulites occur as shear zone bounded lensoidal bodies within low-grade rocks of the South Delhi Terrane and comprise pelitic and calcareous granulites, a gabbro-norite-basic granulite suite and multiple phases of granites of the Ambaji suite. The granulites have undergone three major phases of folding and shearing. The F 1 and F 2 folds are coaxial along NE-SW axis, and F 3 folds are developed across the former along NW-SE axis. Thus, various types of interference patterns are produced. The granulite facies metamorphism is marked by a spinel–cordierite–garnet–sillimanite–quartz assemblage with melt phase and is synkinematic to the F 1 phase of folding. The peak thermobarometric condition is set at ≥850 °C and 5.5–6.8 kb. The granulites have been exhumed through thrusting along multiple ductile shear zones during syn- to post-F 2 folding. Late-stage shearing has produced cataclasites and pseudotachylites. Sensitive High Resolution Ion MicroProbe (SHRIMP) U–Pb dating of zircon from pelitic granulites and synkinematically emplaced granites indicate that: (1) the sedimentary succession of the South Delhi Terrane was deposited between 1240 and 860 Ma with detritus derived from magmatic sources with ages between 1620 and 1240 Ma; (2) folding and granulite metamorphism have taken place between ca. 860 and 800 Ma, and exhumation at around ca. 800–760 Ma; and (3) the last phase of granitic activity occurred at ca. 759 Ma. This shows, for the first time, that the granulites of the South Delhi Terrane are much younger than those of the Sandmata Granulite Complex of the northern part of the Aravalli Mobile Belt, the Saussar granulites of the Central India Mobile Belt and the Eastern Ghats Mobile Belt. Instead, they show similarities to the Neoproterozoic granulites of the Circum Indian Orogens that include the East African Orogen (East Africa and Madagascar), the Southern Granulite Terrane of India and much of Sri Lanka. We suggest that the South Delhi Basin probably marks a trace of the proto-Mozambique Ocean in NW India within Gondwana, that closed when the Marwar Craton, arc fragments (Bemarivo Belt in Madagascar and the Seychelles) and components of the Arabian-Nubian Shield collided with the Aravalli-Bundelkhand Protocontinent at ca. 850–750 Ma.

Transmitted interference effect of double metallic nanoslits composed of a slit and a square-funnel slit

The transmitted interference characteristics for double metallic nanoslits, which are composed of a slit and a square funnel, are investigated by the finite-difference time-domain method. Two types of interference patterns, i.e., the periodic single peak or the periodic double peaks profile, are observed by varying the geometric parameters of the square-funnel slit. The fringe period crucially depends on the exit layer thickness of the square-funnel slit. The near-field field intensity can be enhanced three times that in symmetric slit-doublet structure by selecting specific parameters. We also find that surface plasmon waves can creep along the interface between metal and dielectric, even though the interface possesses orthogonal corners.

Local excitation of surface plasmon in structured Au films by atomic force anodic oxidation

We used a near field scanning optical microscopy (NSOM) to locally excite and detect surface plasmon (SP) in structured Au films by a consecutive process of anodic oxidation of atomic force microscope (AFM) and Au deposition process. Different types of interference patterns with the period close to a half of SP wavelength around and on the array of Au line protrusions are observed in NSOM optical transmission images, depending on the polarization direction of the incident light, which suggests a successful excitation of SP on fabricated nanostructures. The NSOM probes are believed to be somewhat coated with Au during the scans, and these probes are found to be more efficient in exciting SP than uncoated probes. Our result shows that NSOM combined with the AFM anodic oxidation technique provides an efficient and inexpensive method to study the SP excitation on metallic nanostructures.

A neutron spin interferometer using two RF-π/2 flippers

We have developed a neutron spin interferometer using radio frequency (RF) spin flippers. A polarized neutron is split or superposed in the spin space with an RF-π/2 flipper. This interferometer provides three types of interference patterns with high visibility (≳0.9) and high phase resolution (<0.3%) in spite of its simple structure. The principle and structure of the spin interferometer are described and results of performance tests are presented and discussed. The non-homogeneity of an output beam which is expressed as a superposition of two energy eigenstates are demonstrated.

Interferometric technique for determining the energy deposition in gas-flow nuclear-pumped lasers

An interference technique is developed for determining the energy deposition in gas-flow lasers pumped by uranium fission fragments. It is shown that four types of interference patterns may be formed. Algorithms are presented for determining the type of interference and for enumerating the maxima in interference pattern.

The gedanken double-slit experiment with extended incoherent sources

We analyze the influence of the extension of incoherent sources in one- and two-particle double-slit gedanken interferometry of massive particles. For one-particle systems, in the Gaussian-slit approximation, the intensity of the oscillatory term is diminished by an exponential factor. This analytical form differs from that obtained in optics. For two-particle systems we obtain simultaneously one- and two-particle interferences. We compare our approach with other results previously presented in the literature suggesting a type of complementarity between both types of interference patterns.

Interference of Three Electron Waves and Its Application to Direct Visualization of Electric Fields

We present a method for the interference of three electron waves and its application to direct visualization of pure-phase objects such as electromagnetic microfields. Using a transmission electron microscope equipped with a field-emission electron gun and two electron biprisms, an object wave and two reference waves at either side of the object wave are superposed to produce a new type of interference pattern. In this pattern, equal-phase lines of the object wave are directly displayed as intensity modulation of periodic interference fringes. An electric field around a latex particle, induced by electron-beam irradiation, has been observed. The electric charge of the particle is estimated, from an observed phase shift, to be 6.4 × 10 −17C, which is equal to about 400 electrons. A change of the electric field around charged alumina particles at high temperatures has been observed dynamically.

Interference of three electron waves by two biprisms and its application to direct visualization of electromagnetic fields in small regions

We present a method for the interference of three electron waves and its application to direct visualization of pure phase objects such as electromagnetic microfields. Using a transmission electron microscope equipped with a field-emission electron gun and two electron biprisms, an object wave and two reference waves at either side of the object wave are superposed to produce a new type of interference pattern. In this pattern, equal-phase lines of the object wave are directly displayed as intensity modulation of periodic interference fringes. An electric field around a latex particle, induced by electron-beam irradiation, has been observed. The electric charge of the particle is estimated, from observed phase shift, to be 6.4×10−17 C, which is equal to about 400 electrons. A change of the electric field around charged alumina particles at high temperatures has been observed dynamically. Magnetic flux lines emerging from a barium ferrite particle are also visualized.

Direct visualization of electromagnetic microfields by interference of three electron waves

A method is presented for direct visualization of electromagnetic microfields. Using a transmission electron microscope equipped with a field-emission electron gun and two electron biprisms, an object wave and two reference waves are superposed to interfere for producing a new type of interference pattern in which electromagnetic fields are directly observed. Equal-potential lines of an electric field around a latex particle and magnetic flux lines emerging from a barium ferrite particle have been observed.

Acoustic scattering from a fluid-loaded cylindrical shell with discontinuities: Double plate bulkhead

The far-field acoustic scattered pressure from a fluid-loaded cylindrical shell with two internal plate bulkheads is determined from knowledge of the junction forces between the shell and the internal plate structures. Results are shown for the circumferential modes n equals 0 and 2. This paper follows a previous paper in which a single internal plate bulkhead was considered. The approach used to solve for the junction forces is the same as that used in the previous paper. However, the results for the far-field scattered pressure show interesting features that can be associated with the acoustic and structural interaction between the two bulkheads. The interaction is due to both acoustic coupling and structural coupling. The scattered pressure associated with the radial forces at the bulkheads show an interference pattern with high and low intensity regions. The high intensity regions correspond to locations with constructive interference between the components of the scattered pressure by each bulkhead, which have dipolelike radiation characteristics. The low intensity regions correspond to locations with destructive interference. The same type of interference pattern is obtained in the scattered pressure component associated with the radial bending moments. The components of the scattered pressure associated with the bending moment at each bulkhead have quadrupolelike radiation characteristics. However, the contributions of these components is small compared to the other contributions. The scattered pressure components associated with the supersonic, axial longitudinal, and tangential shear waves do not show much of an interference pattern and this is mainly attributed to the fact that the scattering from these supersonic waves has preferred directions of propagation. All components of the scattered pressure show areas of high intensity at very specific frequencies which can only be attributed to structural interaction through the shell between the two internal bulkheads. The far-field scattered pressure results are presented for both bistatic and monostatic scattering.

Hinge migration as a mechanism of superimposed folding

Paraffin wax analogue modelling of superimposed folding shows how early fold shape and orientation determine fold-axis orientation, type of interference pattern and mechanism of superposed folding. During two successive deformations, the behaviour depends on the angle between the first and second compression directions. (i) When they are perpendicular to each other, classic superposed folding with either domes and basins, or folds with vertical axes develop, depending on whether the earlier folds were open or closed. (ii) When the two compression directions are oblique, the earlier folds rotate. The degree of rotation depends on the angle between the first folds and the later compression direction and is proportional to the amount of strain. The orientations of the new folds are close to those of the earlier open folds. The final deformation pattern consists of domains where the orientations of the axes depend on whether the early folds were previously either open or closed. Many early folds are reused to become later folds by the mechanism of hinge migration. These results are consistent with the pattern of superimposed folding observed in the Devoluy structure of the French Alps. They show that simply by studying the directions of fold axes in areas of superposed folding, it is not possible to define compression directions. Moreover there is the possibility that superposed folding may go unnoticed if hinge migration has occurred.

Change of Interference Pattern in the X-Ray Section Topography of Single Crystals with Increasing Dimensions of an Incoherent Source

The role of the non-monochromaticity of the radiation as well as of the source dimensions is analyzed in the X-ray section topography of single crystals. It is shown that for usual experimental conditions when the film is placed directly behind the crystal, the slit in front of the crystal really plays the part of an incoherent source, and the distance between the real source and the crystal has no affect on the interference pattern. A new type of interference pattern is revealed experimentally while changing the slit dimensions. The experimental results agree with theoretical computations. [Russian Text Ignored].

Measurements of Shock Tube Ionization Phenomena by a New Microwave Method

Measured values of electron density and collision frequency in shock-heated argon are presented and compared with theoretical equilibrium values. Both parameters are measured as a function of time during a single shock tube experiment. The measured density at 1 and 3 Torr forepressure equals or exceeds the predicted 1016−1017 electrons per cc at high Mach number (15–18); for lower Mach number, measured values fall far below the calculated curve, showing that loss mechanisms dominate thermal electron production over a significant interval of shock wave flow. The measured collision frequency compares well with the predicted value at 1 Torr but is lower by about an order of magnitude at 3 Torr. The experimental configuration comprises a theta pinch driven shock tube designed to drive a shock front into a coaxial waveguide. Two types of interference patterns are observed by transverse sampling of the longitudinal waves: the first, an anomalous pattern, is interpreted as a resonance caused by electrons ahead of the shock; the second, a well-defined interference between incident and reflected waves, yields measurements of the plasma reflection coefficient magnitude and phase.

Interference Patterns Produced by the Superposition of Folds of Similar Type

The three-dimensional surface forms of the compound structures which result from the superposition of two phases of folding are classified and discussed. The types of interference patterns seen in two dimensional sections are figured and described.