Silicon micromachined high-contrast artificial dielectrics for millimeter-wave transformation optics antennas

Guiding surface electromagnetic waves around disorder without disturbing the wave amplitude or phase is in great demand for modern photonic and plasmonic devices, but is fundamentally difficult to realize because light momentum must be conserved in a scattering event. A partial realization has been achieved by exploiting topological electromagnetic surface states, but this approach is limited to narrow-band light transmission and subject to phase disturbances in the presence of disorder. Recent advances in transformation optics apply principles of general relativity to curve the space for light, allowing one to match the momentum and phase of light around any disorder as if that disorder were not there. This feature has been exploited in the development of invisibility cloaks. An ideal invisibility cloak, however, would require the phase velocity of light being guided around the cloaked object to exceed the vacuum speed of light—a feat potentially achievable only over an extremely narrow band. In this work, we theoretically and experimentally show that the bottlenecks encountered in previous studies can be overcome. We introduce a class of cloaks capable of remarkable broadband surface electromagnetic waves guidance around ultrasharp corners and bumps with no perceptible changes in amplitude and phase. These cloaks consist of specifically designed nonmagnetic metamaterials and achieve nearly ideal transmission efficiency over a broadband frequency range from 0+ to 6 GHz. This work provides strong support for the application of transformation optics to plasmonic circuits and could pave the way toward high-performance, large-scale integrated photonic circuits.

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Resistance Monitor and Control for Vacuum Evaporation of Metals and Carbon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100092827 ◽

1976 ◽

Vol 34 ◽

pp. 572-573

Author(s):

Russell L. Steere ◽

Eric F. Erbe ◽

J. Michael Moseley

Keyword(s):

Electronic Device ◽

Point Sources ◽

High Contrast ◽

Variable Resistor ◽

Quality Of Results ◽

Low Contrast ◽

Evaporation Source ◽

And Control ◽

At Will

We have designed and built an electronic device which compares the resistance of a defined area of vacuum evaporated material with a variable resistor. When the two resistances are matched, the device automatically disconnects the primary side of the substrate transformer and stops further evaporation.This approach to controlled evaporation in conjunction with the modified guns and evaporation source permits reliably reproducible multiple Pt shadow films from a single Pt wrapped carbon point source. The reproducibility from consecutive C point sources is also reliable. Furthermore, the device we have developed permits us to select a predetermined resistance so that low contrast high-resolution shadows, heavy high contrast shadows, or any grade in between can be selected at will. The reproducibility and quality of results are demonstrated in Figures 1-4 which represent evaporations at various settings of the variable resistor.

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Confocal laser microscopy of impregnated central nervous system tissue

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100102559 ◽

1988 ◽

Vol 46 ◽

pp. 94-95

Author(s):

J.N. Turner ◽

M. Siemens ◽

D. Szarowski ◽

D.N. Collins

Keyword(s):

Electron Microscopy ◽

Central Nervous System ◽

Nervous System ◽

Three Dimensional ◽

Dimensional Structure ◽

Confocal Laser ◽

High Contrast ◽

Central Nervous System Tissue ◽

Tissue Samples ◽

Reflected Light

A classic preparation of central nervous system tissue (CNS) is the Golgi procedure popularized by Cajal. The method is partially specific as only a few cells are impregnated with silver chromate usualy after osmium post fixation. Samples are observable by light (LM) or electron microscopy (EM). However, the impregnation is often so dense that structures are masked in EM, and the osmium background may be undesirable in LM. Gold toning is used for a subtle but high contrast EM preparation, and osmium can be omitted for LM. We are investigating these preparations as part of a study to develop correlative LM and EM (particularly HVEM) methodologies in neurobiology. Confocal light microscopy is particularly useful as the impregnated cells have extensive three-dimensional structure in tissue samples from one to several hundred micrometers thick. Boyde has observed similar preparations in the tandem scanning reflected light microscope (TSRLM).

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The CM120 Biotwin: a high-contrast objective lens, optimum cryo-vacuum and improved EDX performance

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100139299 ◽

1995 ◽

Vol 53 ◽

pp. 584-585

Author(s):

Uwe Lücken ◽

Michael Felsmann ◽

Wim M. Busing ◽

Frank de Jong

Keyword(s):

Life Science ◽

Focal Length ◽

Objective Lens ◽

High Contrast ◽

Contrast Imaging ◽

X Ray ◽

Forming Mechanism ◽

Similar Image ◽

High Contrast Imaging ◽

Low Concentrations

A new microscope for the study of life science specimen has been developed. Special attention has been given to the problems of unstained samples, cryo-specimens and x-ray analysis at low concentrations.A new objective lens with a Cs of 6.2 mm and a focal length of 5.9 mm for high-contrast imaging has been developed. The contrast of a TWIN lens (f = 2.8 mm, Cs = 2 mm) and the BioTWTN are compared at the level of mean and SD of slow scan CCD images. Figure 1a shows 500 +/- 150 and Fig. 1b only 500 +/- 40 counts/pixel. The contrast-forming mechanism for amplitude contrast is dependent on the wavelength, the objective aperture and the focal length. For similar image conditions (same voltage, same objective aperture) the BioTWIN shows more than double the contrast of the TWIN lens. For phasecontrast specimens (like thin frozen-hydrated films) the contrast at Scherzer focus is approximately proportional to the √ Cs.

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Performance and applications of the holography electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100151222 ◽

1993 ◽

Vol 51 ◽

pp. 1078-1079

Author(s):

Akira Tonomura

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

Phase Measurement ◽

Electron Holography ◽

Imaging Method ◽

High Contrast ◽

Magnetic Lens ◽

High Brightness ◽

Holographic Imaging ◽

Dynamic Observation

Electron holography is a two-step imaging method. However, the ultimate performance of holographic imaging is mainly determined by the brightness of the electron beam used in the hologram-formation process. In our 350kV holography electron microscope (see Fig. 1), the decrease in the inherently high brightness of field-emitted electrons is minimized by superposing a magnetic lens in the gun, for a resulting value of 2 × 109 A/cm2 sr. This high brightness has lead to the following distinguished features. The minimum spacing (d) of carrier fringes is d = 0.09 Å, thus allowing a reconstructed image with a resolution, at least in principle, as high as 3d=0.3 Å. The precision in phase measurement can be as high as 2π/100, since the position of fringes can be known precisely from a high-contrast hologram formed under highly collimated illumination. Dynamic observation becomes possible because the current density is high.

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Compositional Analysis of III-V Interface Lattice Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600001331 ◽

1980 ◽

Vol 38 ◽

pp. 318-319

Author(s):

A. Olsen ◽

J.C.H. Spence ◽

P. Petroff

Keyword(s):

Crystal Structure ◽

Image Matching ◽

Compositional Analysis ◽

Depth Of Field ◽

Limit Set ◽

High Contrast ◽

Resolution Limit ◽

Fourier Image ◽

Lattice Images ◽

True Structure

Since the point resolution of the JEOL 200CX electron microscope is up = 2.6Å it is not possible to obtain a true structure image of any of the III-V or elemental semiconductors with this machine. Since the information resolution limit set by electronic instability (1) u0 = (2/πλΔ)½ = 1.4Å for Δ = 50Å, it is however possible to obtain, by choice of focus and thickness, clear lattice images both resembling (see figure 2(b)), and not resembling, the true crystal structure (see (2) for an example of a Fourier image which is structurally incorrect). The crucial difficulty in using the information between Up and u0 is the fractional accuracy with which Af and Cs must be determined, and these accuracies Δff/4Δf = (2λu2Δf)-1 and ΔCS/CS = (λ3u4Cs)-1 (for a π/4 phase change, Δff the Fourier image period) are strongly dependent on spatial frequency u. Note that ΔCs(up)/Cs ≈ 10%, independent of CS and λ. Note also that the number n of identical high contrast spurious Fourier images within the depth of field Δz = (αu)-1 (α beam divergence) decreases with increasing high voltage, since n = 2Δz/Δff = θ/α = λu/α (θ the scattering angle). Thus image matching becomes easier in semiconductors at higher voltage because there are fewer high contrast identical images in any focal series.

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Thin Film Inspection with Millimeter-Wave Reflectometer

Research in Nondestructive Evaluation ◽

10.1080/09349849508968223 ◽

1995 ◽

Vol 7 (1) ◽

pp. 89-100

Author(s):

H. C. Han ◽

E. S. Mansueto

Keyword(s):

Thin Film ◽

Millimeter Wave

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