Diffraction effects in spatial and spectral properties of THz radiation from bulk GaAs excited by ultrashort pulses

1995 ◽  
Author(s):  
N. Sarukura ◽  
Z. Liu ◽  
Y. Segawa ◽  
S. Koshihara ◽  
K. Shimoyama ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Ultrashort Pulses ◽  
Thz Radiation ◽  
Bulk Gaas ◽  
Diffraction Effects

dc-electric-field dependence of THz radiation induced by femtosecond optical excitation of bulk GaAs

1994 ◽  
Vol 49 (3) ◽  
pp. 2234-2237 ◽  
Author(s):  
B. B. Hu ◽  
A. S. Weling ◽  
D. H. Auston ◽  
A. V. Kuznetsov ◽  
C. J. Stanton
Keyword(s):  
Electric Field ◽  
Field Dependence ◽  
Optical Excitation ◽  
Thz Radiation ◽  
Bulk Gaas ◽  
Electric Field Dependence ◽  
Dc Electric Field ◽  
Radiation Induced

Degradation and Destruction of Thin Steel Films under Repeated Exposure to Ultrashort Pulses of THz Radiation

2019 ◽  
Vol 45 (6) ◽  
pp. 570-572
Author(s):  
O. V. Chefonov ◽  
A.V. Ovchinnikov ◽  
S. A. Evlashin ◽  
M. B. Agranat
Keyword(s):  
Ultrashort Pulses ◽  
Repeated Exposure ◽  
Thz Radiation ◽  
Thin Steel

Discovery and Measurement of Double Stars by Lunar Occultations

1965 ◽  
Vol 5 ◽  
pp. 28-37
Author(s):  
R. Edward Nather ◽  
David S. Evans
Keyword(s):  
The Moon ◽  
Double Stars ◽  
Stellar Diameters ◽  
Diffraction Effects

When a star is occulted by the dark limb of the Moon its apparent intensity drops to zero very quickly. MacMahon (1909) proposed that the time of disappearance would measure the diameter of the star, but Eddington (1909) demonstrated that diffraction effects at the lunar limb would lengthen the apparent time of disappearance to about 20 msec, and suggested that these effects would greatly limit the usefulness of the technique. MacMahon’s paper indicates that he was aware that stellar duplicity could be detected from occultation observations, but he did not amplify the point and Eddington did not comment on it. While it has been demonstrated theoretically by Williams (1939) and experimentally by Whitford (1939) and others that stellar diameters of a few arcmsec can be measured by this technique, its use for the discovery and measurement of double stars has been only incidental to other programs (O’Keefe and Anderson, 1952; Evanset al., 1954). Properly exploited, the method can contribute materially to the study of double stars.

Transmission Electron Diffraction Analysis by Computer

1970 ◽  
Vol 28 ◽  
pp. 40-41
Author(s):  
R.A. Ploc ◽  
G.H. Keech
Keyword(s):  
Electron Diffraction ◽  
Input Data ◽  
Reciprocal Lattice ◽  
Computer Programme ◽  
Transmission Electron Diffraction ◽  
Usual Procedure ◽  
Transmission Electron ◽  
Complex Shapes ◽  
Computer Input ◽  
Diffraction Effects

An unambiguous analysis of transmission electron diffraction effects requires two samplings of the reciprocal lattice (RL). However, extracting definitive information from the patterns is difficult even for a general orthorhombic case. The usual procedure has been to deduce the approximate variables controlling the formation of the patterns from qualitative observations. Our present purpose is to illustrate two applications of a computer programme written for the analysis of transmission, selected area diffraction (SAD) patterns; the studies of RL spot shapes and epitaxy.When a specimen contains fine structure the RL spots become complex shapes with extensions in one or more directions. If the number and directions of these extensions can be estimated from an SAD pattern the exact spot shape can be determined by a series of refinements of the computer input data.

Characteristic Geometry and Diffraction Contrast of Dispersed ThO2 Crystals

1969 ◽  
Vol 27 ◽  
pp. 168-169
Author(s):  
R. J. Horylev ◽  
L. E. Murr
Keyword(s):  
Dark Field ◽  
Particle Orientation ◽  
Contrast Effects ◽  
Strain Fields ◽  
Diffraction Contrast ◽  
Dispersed Particles ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Particle Images ◽  
Diffraction Effects

Smith has shown by dark-field electron microscopy of extracted ThO2 particles from TD-nickel (2% ThO2) that they possess single crystal characteristics. It is generally assumed that these particle dispersions are incoherent. However, some diffraction effects associated with the particle images appeared to be similar to coherency strain fields. The present work will demonstrate conclusively that ThO2 dispersed particles in TD-nickel (2% ThO2) and TD-NiCr (2% ThO2, 20% Cr, Ni) are single crystals. Moreover, the diffraction contrast effects are extinction fringes. That is, these effects arise because of the particle orientation with respect to the electron beam and the extinction conditions for various operating reflections The particles are in fact incoherent.

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