Rigorous Bragg condition for volume holographic gratings with anisotropic distortion

In the Study of small metal particles the shape is a very Important parameter. Using electron microscopy Ino and Owaga(l) have studied the shape of twinned particles of gold. In that work electron diffraction and contrast (dark field) experiments were used to produce models of a crystal particle. In this work we report a method which can give direct information about the shape of an small metal particle in the amstrong- size range with high resolution. The diffraction pattern of a sample containing small metal particles contains in general several systematic and non- systematic reflections and a two-beam condition can not be used in practice. However a N-beam condition produces a reduced extinction distance. On the other hand if a beam is out of the bragg condition the effective extinction distance is even more reduced.

Download Full-text

Spacings and Intensities of Weak-Beam Dark Field Thickness Fringes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100097685 ◽

1981 ◽

Vol 39 ◽

pp. 222-223

Author(s):

M. Avalos-Borja ◽

K. Heinemann

Keyword(s):

Selection Criterion ◽

Dark Field ◽

Dynamical Theory ◽

Bragg Condition ◽

Weak Beam ◽

Kinematical Theory ◽

Equal Thickness

Weak-beam dark field (WBDF) TEM produces narrowly spaced equal-thickness fringes in wedge-shaped crystals. Using non-systematic diffraction conditions, we have shown elsewhere that simple 2-beam kinematical theory (KT) calculations yield average fringe spacings that are for most practical purposes as satisfactorily accurate as the average spacings obtained from optimized multibeam dynamical theory (DT) calculations, As Fig. 1 shows, this result holds for deviations from the Bragg condition as low as 2x10-1 nm-1, and the differences between the results from the two calculational methods become increasingly insignificant for larger excitation errors. (Unless otherwise noted, all results reported here are for gold crystals, using the 200 beam at 100 KV; the DT calculations were made for 74 beams, using the selection criterion D as discussed in ref. [3]).

Download Full-text

Multislice calculations of RHEED patterns from vicinal Si (001)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150836 ◽

1993 ◽

Vol 51 ◽

pp. 1000-1001

Author(s):

Scott Lordi

Keyword(s):

Misorientation Angle ◽

Incident Angle ◽

Incident Beam ◽

Experimental Results ◽

Bragg Condition ◽

Vicinal Surfaces ◽

Kinematic Theory ◽

Step Edges

Vicinal Si (001) surfaces are interesting because they are good substrates for the growth of III-V semiconductors. Spots in RHEED patterns from vicinal surfaces are split due to scattering from ordered step arrays and this splitting can be used to determine the misorientation angle, using kinematic arguments. Kinematic theory is generally regarded to be inadequate for the calculation of RHEED intensities; however, only a few dynamical RHEED simulations have been attempted for vicinal surfaces. The multislice formulation of Cowley and Moodie with a recently developed edge patching method was used to calculate RHEED patterns from vicinal Si (001) surfaces. The calculated patterns are qualitatively similar to published experimental results and the positions of the split spots quantitatively agree with kinematic calculations.RHEED patterns were calculated for unreconstructed (bulk terminated) Si (001) surfaces misoriented towards [110] ,with an energy of 15 keV, at an incident angle of 36.63 mrad ([004] bragg condition), and a beam azimuth of [110] (perpendicular to the step edges) and the incident beam pointed down the step staircase.

Download Full-text

Three-dimensional coupled wave study for finite-sized anisotropic volume holographic gratings under ultrashort pulsed beam readout

Journal of the Optical Society of America A ◽

10.1364/josaa.24.001799 ◽

2007 ◽

Vol 24 (6) ◽

pp. 1799 ◽

Cited By ~ 2

Author(s):

Chunhua Wang ◽

Liren Liu ◽

Aimin Yan ◽

Dean Liu ◽

Yu Zhou ◽

...

Keyword(s):

Three Dimensional ◽

Holographic Gratings ◽

Coupled Wave

Download Full-text

Polarization holographic gratings in PAZO polymer films doped with particles of biometals

Journal of Photochemistry and Photobiology A Chemistry ◽

10.1016/j.jphotochem.2021.113196 ◽

2021 ◽

Vol 411 ◽

pp. 113196

Author(s):

A. Stoilova ◽

G. Mateev ◽

D. Nazarova ◽

L. Nedelchev ◽

E. Stoykova ◽

...

Keyword(s):

Polymer Films ◽

Holographic Gratings

Download Full-text

Holographic Recording Performance of Acrylate-Based Photopolymer under Different Preparation Conditions for Waveguide Display

Polymers ◽

10.3390/polym13060936 ◽

2021 ◽

Vol 13 (6) ◽

pp. 936

Author(s):

Zhongwen Shen ◽

Yishi Weng ◽

Yuning Zhang ◽

Chuang Wang ◽

Ao Liu ◽

...

Keyword(s):

Augmented Reality ◽

Diffraction Efficiency ◽

Green Light ◽

Holographic Recording ◽

Holographic Gratings ◽

Preparation Conditions

This work proposes a green light-sensitive acrylate-based photopolymer. The effects of the preparation conditions for the waveguide applied volume holographic gratings (VHGs) were experimentally investigated. The optimum preparation conditions for holographic recording were revealed. After optimization, the peak of VHG diffraction efficiency reached 99%, the diffractive wavelength bandwidth increased from 13 nm to 22 nm, and the corresponding RIM was 0.06. To prove the wide application prospect of the acrylate-based photopolymer in head-mounted augmented reality (AR) displays, green monochromatic volume holographic waveguides were fabricated. The display results showed that the prototype was able to achieve a 28° diagonal FOV and possessed a system luminance of 300 cd/m2.

Download Full-text