“Acceptor impurity” mode in 1-D holographic photonic crystals achieved by controlling polarization state of the incident beam

AbstractA ray-optics model is proposed to describe the vector beam transformation in a strongly focusing optical system. In contrast to usual approaches based on the focused field distribution near the focal plane, we use the beam pattern formed immediately after the exit aperture. In this cross section, details of the output field distribution are of minor physical interest but proper allowance is made for transformation of the beam polarization state. This enables the spin and orbital angular momentum representations to be obtained, which are valid for any cross section of the transformed beam. Simple analytical results are available for a transversely homogeneous, circularly polarized incident beam confined by a circular aperture. Variations of the spin and orbital angular momenta of the output beam with change of the focusing strength are analyzed. The analytical results are in good qualitative and reasonable quantitative agreement with the results of numerical calculations performed for the Gaussian and Laguerre-Gaussian beams. The model supplies an efficient and physically transparent means for qualitative analysis of the spin-to-orbital angular momentum conversion. It can be generalized to incident beams with complex spatial and polarization structure.

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MULTI-REFRACTION WITH SAME POLARIZATION STATE IN TWO DIMENSIONAL TRIANGULAR PHOTONIC CRYSTALS

Progress In Electromagnetics Research ◽

10.2528/pier12040306 ◽

2012 ◽

Vol 128 ◽

pp. 91-103 ◽

Cited By ~ 3

Author(s):

Guoyan Dong ◽

Ji Zhou ◽

Xiulun Yang ◽

Xiangfeng Meng

Keyword(s):

Photonic Crystals ◽

Polarization State ◽

Two Dimensional

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Instrument-independent specification of the diffraction geometry and polarization state of the incident X-ray beam

Journal of Applied Crystallography ◽

10.1107/s0021889808038521 ◽

2008 ◽

Vol 42 (1) ◽

pp. 101-108 ◽

Cited By ~ 4

Author(s):

Marc Schiltz ◽

Gérard Bricogne

Keyword(s):

Bragg Reflection ◽

Polarization State ◽

Azimuthal Angle ◽

Incident Beam ◽

Stokes Parameters ◽

Anomalous Scattering ◽

X Ray ◽

Data Processing Software ◽

Diffraction Geometry ◽

Definition Of

This work augments the proposal of Schwarzenbach & Flack [J. Appl. Cryst.(1989),22, 601–605], who have advocated the use of a diffractometer-independent definition of the azimuthal angle ψ to specify the diffraction geometry of a Bragg reflection. It is here proposed that one additional angle ξ, which is also based on a diffractometer-independent definition, is needed to encode the direction of linear polarization for those experiments where this quantity is of importance. This definition is then extended to the cases of partially and/or elliptically polarized X-ray beams, and the use of three normalized Stokes parameters,P1,P2andP3, together with ξ, is advocated in order to characterize exhaustively the polarization state of the incident beam. The conventions proposed here present a general, unambiguous and economical means of encoding the information about the diffraction geometry, without the need to record any further information about the instrument, crystal orientation matrix and goniometer angles. Data-processing software using these definitions to analyse polarization-dependent phenomena becomes instrument-independent and completely general. These methods have been implemented in the macromolecular phasing programSHARPfor exploiting the polarization anisotropy of anomalous scattering in protein crystals.

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Shifts of Coherent Light Beams on Reflection at Plane Interfaces between Isotropic Media

Australian Journal of Physics ◽

10.1071/ph800319a ◽

1980 ◽

Vol 33 (2) ◽

pp. 319 ◽

Cited By ~ 10

Author(s):

RG Turner

Keyword(s):

Large Range ◽

Polarization State ◽

Incident Beam ◽

Theoretical Work ◽

Beam Profile ◽

Theoretical Treatment ◽

Coherent Light ◽

Theoretical Approaches ◽

Isotropic Media ◽

Light Beams

Previous experimental and theoretical work on both longitudinal and transverse shifts of light beams at totally reflecting interfaces is briefly reviewed and the discrepancy between the predictions of the two principal theoretical approaches is discussed. A theoretical treatment, valid for an interface between any two media, is presented. The intensity profile of the reflected beam is the same as that of the incident beam (albeit shifted in the reflecting interface) only for certain polarization states of the incident beam and provided that the reflection parameters of the interface meet certain conditions. If these conditions are not met the reflected beam profile suffers distortion and, possibly, deviation from its expected direction. Because the polarization state of a beam is, in general, altered by reflection, measurements of the shifts over a large range of angles of incidence at a single reflection are needed in order to verify the predictions.

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Jet-based Photonic Crystals for Terahertz Technology – A Need for Higher Resolution

MRS Proceedings ◽

10.1557/proc-860-ll4.3 ◽

2004 ◽

Vol 860 ◽

Author(s):

Jin Li ◽

Thomas M. Horgan ◽

Andrew J. Gatesman ◽

Robert H. Giles ◽

Aram S. Karakashian ◽

...

Keyword(s):

Photonic Crystals ◽

Electromagnetic Waves ◽

Imaging System ◽

Incident Beam ◽

Fold Increase ◽

Dielectric Constants ◽

Frequency Domain Method ◽

System A ◽

Ft Ir ◽

Terahertz Lasers

ABSTRACTTwo-dimensional hexagonal photonic crystals of air columns in a wax substrate were fabricated by jet-based methods. By modifying the structure of the photonic crystals (PC), electromagnetic waves can be controlled, enabling the design of novel devices for waveguides, filters, and couplers. The jet-based processing is a solid freeforming method that can fabricate complex 2D or 3D photonic structures quickly and easily as compared to micro-machining and lithographic methods. The resolution of our 3D Systems ThermoJet® solider object printer is 300 × 400 × 600 dpi (XYZ) with the layer thickness of 0.042 mm. The wax used is a thermopolymer build material, similar to production investment casting wax material. The periodicity of the lattice of our 2D PC structures was designed to form bandstop filters in the 0.1–0.3 THz range. Transmission spectra of the structures were measured with a Bruker IFS 66v FT-IR interferometer. Photonic band gaps were observed at 0.17 THz and 0.23 THz along the Γ-M direction for both the TM and TE polarized incident beam for the PC structures with lattice constant of 0.787 mm and 0.586 mm, respectively. The location and width of the bandgaps agree with theoretical calculation based on a block-iterative frequency-domain method for Maxwell's equations in a planewave basis. To the best of our knowledge, this is the first time a jet-based process has been used successfully to fabricate PC structures at these high frequencies. However, the ThermoJet® printer as well as other current available solid freeforming technologies lack the resolution to PC structures operating in the terahertz regime. To extend this technology to terahertz applications, such as terahertz lasers, waveguides, and imaging system, a 10-fold increase in machine resolution is required to produce finer structures. Engineering materials with lower electromagnetic absorption and higher dielectric constants at terahertz frequencies are also critical to developing THz photonic bandgap technology.

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Instrumentation for detecting channelling radiation in the high-voltage electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075385 ◽

1983 ◽

Vol 41 ◽

pp. 318-319

Author(s):

J. H. Butler ◽

C. J. Humphreys

Keyword(s):

Monochromatic Light ◽

Incident Beam ◽

Laboratory Frame ◽

Relativistic Electrons ◽

Voltage Electron ◽

Dipole Emission ◽

Sinusoidal Oscillations ◽

Pass Through ◽

Incident Beam Energy ◽

Increasing Function

Electromagnetic radiation is emitted when fast (relativistic) electrons pass through crystal targets which are oriented in a preferential (channelling) direction with respect to the incident beam. In the classical sense, the electrons perform sinusoidal oscillations as they propagate through the crystal (as illustrated in Fig. 1 for the case of planar channelling). When viewed in the electron rest frame, this motion, a result of successive Bragg reflections, gives rise to familiar dipole emission. In the laboratory frame, the radiation is seen to be of a higher energy (because of the Doppler shift) and is also compressed into a narrower cone of emission (due to the relativistic “searchlight” effect). The energy and yield of this monochromatic light is a continuously increasing function of the incident beam energy and, for beam energies of 1 MeV and higher, it occurs in the x-ray and γ-ray regions of the spectrum. Consequently, much interest has been expressed in regard to the use of this phenomenon as the basis for fabricating a coherent, tunable radiation source.

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Arsenic segregation in polysilicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100074604 ◽

1983 ◽

Vol 41 ◽

pp. 154-155 ◽

Cited By ~ 1

Author(s):

P.E. Batson ◽

C.R.M. Grovenor ◽

D.A. Smith ◽

C. Wong

Keyword(s):

Incident Beam ◽

Silicon Wafers ◽

Chemical Polishing ◽

Bright Field Image ◽

Beam Size ◽

Stem Analysis ◽

Bright Field ◽

Twin Boundaries ◽

X Ray ◽

Line Scan

In this work As doped polysilicon was deposited onto (100) silicon wafers by APCVD at 660°C from a silane-arsine mixture, followed by a ten minute anneal at 1000°C, and in one case a further ten minute anneal at 700°C. Specimens for TEM and STEM analysis were prepared by chemical polishing. The microstructure, which is unchanged by the final 700°C anneal,is shown in Figure 1. It consists of numerous randomly oriented grains many of which contain twins.X-ray analysis was carried out in a VG HB5 STEM. As K α x-ray counts were collected from STEM scans across grain and twin boundaries, Figures 2-4. The incident beam size was about 1.5nm in diameter, and each of the 20 channels in the plots was sampled from a 1.6nm length of the approximately 30nm line scan across the boundary. The bright field image profile along the scanned line was monitored during the analysis to allow correlation between the image and the x-ray signal.

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Resolution Attainable With the Present Day STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071594 ◽

1973 ◽

Vol 31 ◽

pp. 230-231 ◽

Cited By ~ 1

Author(s):

J. S. Wall ◽

J. P. Langmore ◽

H. Isaacson ◽

A. V. Crewe

Keyword(s):

Spherical Aberration ◽

Focal Length ◽

Incident Beam ◽

Scanning Transmission Electron Microscope ◽

Aperture Size ◽

Magnetic Lens ◽

Peak Intensity ◽

Transmission Electron ◽

Scanning Transmission ◽

Half Angle

The scanning transmission electron microscope (STEM) constructed by the authors employs a field emission gun and a 1.15 mm focal length magnetic lens to produce a probe on the specimen. The aperture size is chosen to allow one wavelength of spherical aberration at the edge of the objective aperture. Under these conditions the profile of the focused spot is expected to be similar to an Airy intensity distribution with the first zero at the same point but with a peak intensity 80 per cent of that which would be obtained If the lens had no aberration. This condition is attained when the half angle that the incident beam subtends at the specimen, 𝛂 = (4𝛌/Cs)¼

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Symmetries and Extinction Rules in CBED

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055758 ◽

1982 ◽

Vol 40 ◽

pp. 684-685

Author(s):

K. Ishizuka

Keyword(s):

Electron Diffraction ◽

Incident Beam ◽

Convergent Beam Electron Diffraction ◽

Beam Direction ◽

Beam Electron ◽

Convergent Beam

The technique of convergent-beam electron diffraction (CBED) has been established. However there is a distinct discrepancy concerning the CBED pattern symmetries associated with translation symmetries parallel to the incident beam direction: Buxton et al. assumed no detectable effects of translation components, while Goodman predicted no associated symmetries. In this report a procedure used by Gjønnes & Moodie1 to obtain dynamical extinction rules will be extended in order to derive the CBED pattern symmetries as well as the dynamical extinction rules.

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