scholarly journals Diffractive Geometric Optics for Bloch Wave Packets

2011 ◽  
Vol 202 (2) ◽  
pp. 373-426 ◽  
Author(s):  
Grégoire Allaire ◽  
Mariapia Palombaro ◽  
Jeffrey Rauch
Keyword(s):  
Wave Packets ◽  
Bloch Wave ◽  
Geometric Optics

Acoustic Behavior of Near Periodic Elastic Structures

1995 ◽  
Author(s):  
Douglas M. Photiadis
Keyword(s):  
Cross Section ◽  
Wave Packets ◽  
Acoustic Scattering ◽  
Direct Interaction ◽  
Bloch Wave ◽  
Acoustic Properties ◽  
Theoretical Development ◽  
Naval Research ◽  
Bragg Scattering ◽  
Elastic Structures

Abstract Near periodic arrays of discontinuities have been predicted to have a significant impact on the acoustic properties of elastic structures. The discontinuities in the elastic properties of the structure produce a characteristic signature in the acoustic scattering cross section of the structure via two distinct mechanisms; a direct interaction producing acoustic Bragg scattering, and an indirect interaction wherein the discontinuities fundamentally alter the free waves of the structure. The locally propagating states of the pseudo-periodic system are Floquet or Bloch wave packets and the locations of the highlights in the cross section may be determined simply from the Bloch wavenumber via a phase matching argument. Predicting the resulting scattering levels requires an understanding of the propagation of the Bloch wave packets in the finite, pseudo-periodic structure. In the case of a thin ribbed cylindrical shell or plate this scattering mechanism can arise from flexural waves, and recent experimental results obtained at Naval Research Laboratory have demonstrated the importance of both this mechanism and Bragg scattering on the acoustic far field over a broad frequency range. In this paper, these results and the underlying theoretical development will be discussed.

Bloch Wave Packets in Semiconductor Superlattices: Composition and Spatial Displacement

1998 ◽  
Vol 206 (1) ◽  
pp. 315-324 ◽  
Author(s):  
F. L�ser ◽  
M. Sudzius ◽  
V.G. Lyssenko ◽  
T. Hasche ◽  
K. Leo ◽  
...  
Keyword(s):  
Wave Packets ◽  
Bloch Wave ◽  
Spatial Displacement ◽  
Semiconductor Superlattices

scholarly journals A bound on the group velocity for Bloch wave packets

2015 ◽  
Vol 72 (2) ◽  
pp. 119-123
Author(s):  
Grégoire Allaire ◽  
Mariapia Palombaro ◽  
Jeffrey Rauch
Keyword(s):  
Group Velocity ◽  
Wave Packets ◽  
Bloch Wave

scholarly journals Dynamics of semiclassical Bloch wave packets

2007 ◽  
Vol 151 (3) ◽  
pp. 791-802 ◽  
Author(s):  
P. A. Horváthy ◽  
L. Martina
Keyword(s):  
Wave Packets ◽  
Bloch Wave

Generation and manipulation of Bloch wave packets

2000 ◽  
Vol 7 (1-2) ◽  
pp. 285-288 ◽  
Author(s):  
F. Löser ◽  
M. Sudzius ◽  
B. Rosam ◽  
V.G. Lyssenko ◽  
Y. Kosevich ◽  
...  
Keyword(s):  
Wave Packets ◽  
Bloch Wave

Motion of Bloch Wave Packets

1987 ◽  
Vol 35 (6) ◽  
pp. 859-867 ◽  
Author(s):  
J N Churchill ◽  
F E Holmstrom
Keyword(s):  
Wave Packets ◽  
Bloch Wave

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.

Convergent-beam electron diffraction at high spatial resolution

1992 ◽  
Vol 50 (2) ◽  
pp. 1152-1153 ◽  
Author(s):  
J W Steeds
Keyword(s):  
Electron Diffraction ◽  
High Temperature Superconductors ◽  
Bloch Wave ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Energy Filtering ◽  
Small Probe ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Convergent Beam

That the techniques of convergent beam electron diffraction (CBED) are now widely practised is evident, both from the way in which they feature in the sale of new transmission electron microscopes (TEMs) and from the frequency with which the results appear in the literature: new phases of high temperature superconductors is a case in point. The arrival of a new generation of TEMs operating with coherent sources at 200-300kV opens up a number of new possibilities.First, there is the possibility of quantitative work of very high accuracy. The small probe will essentially eliminate thickness or orientation averaging and this, together with efficient energy filtering by a doubly-dispersive electron energy loss spectrometer, will yield results of unsurpassed quality. The Bloch wave formulation of electron diffraction has proved itself an effective and efficient method of interpreting the data. The treatment of absorption in these calculations has recently been improved with the result that <100> HOLZ polarity determinations can now be performed on III-V and II-VI semiconductors.

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