On the analogy between Fresnel diffraction and dispersion in transmission lines and some of its applications

2008 ◽  
Author(s):  
Pierre Pellat-Finet ◽  
Zandra Lizarazo ◽  
Rafael Torres ◽  
Niklaus Ursus Wetter ◽  
Jaime Frejlich
Keyword(s):  
Transmission Lines ◽  
Fresnel Diffraction

Observation of Phase Contrast Images in STEM and CTEM Modes by Using 100 kV Field Emission Electron Gun

1974 ◽  
Vol 32 ◽  
pp. 390-391
Author(s):  
Y. Harada ◽  
T. Goto ◽  
H. Koike ◽  
T. Someya
Keyword(s):  
Field Emission ◽  
Phase Contrast ◽  
Image Formation ◽  
Fresnel Diffraction ◽  
Experimental Results ◽  
Electron Gun ◽  
Scanning Microscopy ◽  
Emission Electron ◽  
Lattice Images

Since phase contrasts of STEM images, that is, Fresnel diffraction fringes or lattice images, manifest themselves in field emission scanning microscopy, the mechanism for image formation in the STEM mode has been investigated and compared with that in CTEM mode, resulting in the theory of reciprocity. It reveals that contrast in STEM images exhibits the same properties as contrast in CTEM images. However, it appears that the validity of the reciprocity theory, especially on the details of phase contrast, has not yet been fully proven by the experiments. In this work, we shall investigate the phase contrast images obtained in both the STEM and CTEM modes of a field emission microscope (100kV), and evaluate the validity of the reciprocity theory by comparing the experimental results.

Simulation of high-resolution annular dark field STEM images

1995 ◽  
Vol 53 ◽  
pp. 40-41
Author(s):  
E. J. Kirkland
Keyword(s):  
Electron Beam ◽  
Atomic Layer ◽  
Fresnel Diffraction ◽  
Dark Field ◽  
Objective Lens ◽  
Image Simulation ◽  
Small Probe ◽  
Annular Dark Field ◽  
Stem Image ◽  
Uniform Plane

In a STEM an electron beam is focused into a small probe on the specimen. This probe is raster scanned across the specimen to form an image from the electrons transmitted through the specimen. The objective lens is positioned before the specimen instead of after the specimen as in a CTEM. Because the probe is focused and scanned before the specimen, accurate annular dark field (ADF) STEM image simulation is more difficult than CTEM simulation. Instead of an incident uniform plane wave, ADF-STEM simulation starts with a probe wavefunction focused at a specified position on the specimen. The wavefunction is then propagated through the specimen one atomic layer (or slice) at a time with Fresnel diffraction between slices using the multislice method. After passing through the specimen the wavefunction is diffracted onto the detector. The ADF signal for one position of the probe is formed by integrating all electrons scattered outside of an inner angle large compared with the objective aperture.

Composite right/left-handed transmission line with array of thermocouples for generating terahertz radiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20502
Author(s):  
Behrokh Beiranvand ◽  
Alexander S. Sobolev ◽  
Anton V. Kudryashov
Keyword(s):  
Transmission Line ◽  
Terahertz Radiation ◽  
Transmission Lines ◽  
Software Package ◽  
Optical Pulses ◽  
Capacitively Coupled ◽  
Voltage Difference ◽  
Left Handed ◽  
Microwave Transmission ◽  
Commercial Software Package

We present a new concept of the thermoelectric structure that generates microwave and terahertz signals when illuminated by femtosecond optical pulses. The structure consists of a series array of capacitively coupled thermocouples. The array acts as a hybrid type microwave transmission line with anomalous dispersion and phase velocity higher than the velocity of light. This allows for adding up the responces from all the thermocouples in phase. The array is easily integrable with microstrip transmission lines. Dispersion curves obtained from both the lumped network scheme and numerical simulations are presented. The connection of the thermocouples is a composite right/left-handed transmission line, which can receive terahertz radiation from the transmission line ports. The radiation of the photon to the surface of the thermocouple structure causes a voltage difference with the bandwidth of terahertz. We examined a lossy composite right/left-handed transmission line to extract the circuit elements. The calculated properties of the design are extracted by employing commercial software package CST STUDIO SUITE.

Time-domain analysis of dispersive transmission lines

1993 ◽  
Vol 3 (3) ◽  
pp. 581-591 ◽  
Author(s):  
Wojciech Gwarek ◽  
Malgorzata Celuch-Marcysiak
Keyword(s):  
Transmission Lines ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis

Fresnel diffraction by a Round aperture

1970 ◽  
Vol 102 (12) ◽  
pp. 655-656
Author(s):  
L.I. Vidro ◽  
Yu.P. Basharov ◽  
A.E. Kudryashov
Keyword(s):  
Fresnel Diffraction
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