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This paper presents a system-level efficiency analysis, a rapid design methodology, and a numerical demonstration of efficient sub-micron, spin-wave transducers in a microwave system. Applications such as Boolean spintronics, analog spin-wave-computing, and magnetic microwave circuits are expected to benefit from this analysis and design approach. These applications have the potential to provide a low-power, magnetic paradigm alternative to modern electronic systems, but they have been stymied by a limited understanding of the microwave, system-level design for spin-wave circuits. This paper proposes an end-to-end microwave/spin-wave system model that permits the use of classical microwave network analysis and matching theory towards analyzing and designing efficient transduction systems. This paper further compares magnetostatic-wave transducer theory to electromagnetic simulations and finds close agreement, indicating that the theory, despite simplifying assumptions, is useful for rapid yet accurate transducer design. It further suggests that the theory, when modified to include the exchange interaction, will also be useful to rapidly and accurately design transducers launching magnons at exchange wavelengths. Comparisons are made between microstrip and co-planar waveguide lines, which are expedient, narrowband, and low-efficiency transducers, and grating and meander lines that are capable of high-efficiency and wideband performance. The paper concludes that efficient microwave-to-spin-wave transducers are possible and presents a meander transducer design on YIG capable of launching λ = 500 nm spin waves with an efficiency of − 4.45 dB and a 3 dB-bandwidth of 134 MHz.

This paper reports a two-orders-of-magnitude improvement in the sensitivity of antenna-coupled nanothermocouple (ACNTC) infrared detectors. The electrical signal generated by on-chip ACNTCs results from the temperature difference between a resonant antenna locally heated by infrared radiation and the substrate. A cavity etched under the antenna provides two benefits. It eliminates the undesirable cooling of the hot junction by thermally isolating the antenna from the substrate. More importantly, careful cavity design results in constructive interference of the incident radiation reflected back to the antenna, which significantly increases the detector sensitivity. We present the cavity-depth-dependent response of ACNTCs with cavity depths between 1 μm and 22 μm. When constructive interference is maximized, the thermal response increases by 100-fold compared to devices without the cavity.

We investigate the generation of electrical signals by suspended thermoelectrically coupled nanoantennas (TECNAs) above a quasi-spherical reflector cavity in response to rapidly changing long-wave infrared radiation. These sensors use a resonant nanoantenna to couple the IR energy to a nanoscale thermocouple. They are positioned over a cavity, etched into the Si substrate, that provides thermal isolation and is designed as an optical element to focus the IR radiation to the antenna. We study the frequency-dependent response of such TECNAs to amplitude-modulated 10.6 μm IR signals. We experimentally demonstrate response times on the order of 3 μs, and a signal bandwidth of about 300 kHz. The observed electrical response is in excellent correlation with finite element method simulations based on the thermal properties of nanostructures. Both experiments and simulations show a key trade-off between sensitivity and response time for such structures and provide solutions for specific target applications.

When simulating sky images, one often takes a galaxy image F(x) defined by a set of pixelized samples and an interpolation kernel, and then wants to produce a new sampled image representing this galaxy as it would appear with a different point-spread function, a rotation, shearing, or magnification, and/or a different pixel scale. These operations are sometimes only possible, or most efficiently executed, as resamplings of the Fourier transform F ˜ ( u ) of the image onto a u-space grid that differs from the one produced by a discrete Fourier transform (DFT) of the samples. In some applications, it is essential that the resampled image be accurate to better than one part in 103, so in this paper, we first use standard Fourier techniques to show that Fourier-domain interpolation with a wrapped sinc function yields the exact value of F ˜ ( u ) in terms of the input samples and kernel. This operation scales with image dimension as N4 and can be prohibitively slow, so we next investigate the errors accrued from approximating the sinc function with a compact kernel. We show that these approximations produce a multiplicative error plus a pair of ghost images (in each dimension) in the simulated image. Standard Lanczos or cubic interpolators, when applied in Fourier domain, produce unacceptable artifacts. We find that errors less than one part in 103 can be obtained by (1) fourfold zero-padding of the original image before executing the x → u DFT, followed by (2) resampling to the desired u-grid using a six-point, piecewise-quintic interpolant that we design expressly to minimize the ghosts, then (3) executing the DFT back to x-domain.

ABSTRACT The wavelength dependence of atmospheric refraction causes elongation of finite-bandwidth images along the elevation vector, which produces spurious signals in weak gravitational lensing shear measurements unless this atmospheric dispersion is calibrated and removed to high precision. Because astrometric solutions and point spread function (PSF) characteristics are typically calibrated from stellar images, differences between the reference stars' spectra and the galaxies' spectra will leave residual errors in both the astrometric positions ( Δ R ¯ ) and in the second moment (width) of the wavelength-averaged PSF (ΔV) for galaxies. We estimate the level of ΔV that will induce spurious weak lensing signals in PSF-corrected galaxy shapes that exceed the statistical errors of the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST) cosmic-shear experiments. We also estimate the Δ R ¯ signals that will produce unacceptable spurious distortions after stacking of exposures taken at different air masses and hour angles. Using standard galaxy and stellar spectral templates we calculate the resultant errors in the griz bands and find that atmospheric dispersion shear systematics, left uncorrected, are up to 6 and 2 times larger in g and r bands, respectively, than the thresholds at which they become significant contributors to the DES error budget, but can be safely ignored in i and z bands. For the stricter LSST requirements, the factors are about 30, 10, and 3 in g, r, and i bands, respectively. These shear systematic errors scale with observed zenith angle z as 〈 tan2 z〉, for which we take a nominal value of unity-simulations of DES and LSST suggest 0.6-1.0. We find that a simple correction linear in galaxy color is accurate enough to reduce dispersion shear systematics to insignificant levels in the r band for DES and i band for LSST, but still as much 5× above the threshold of significance for LSST r-band observations. More complex approaches to correction of the atmospheric dispersion signal will likely be able to reduce the systematic cosmic shear errors below statistical errors for LSST r band. But g-band dispersion effects remain large enough that it seems likely that induced systematics will dominate the statistical errors of both surveys, and cosmic-shear measurements should rely on the redder bands.

A functioning logic gate based on quantum-dot cellular automata is presented, where digital data are encoded in the positions of only two electrons. The logic gate consists of a cell, composed of four dots connected in a ring by tunnel junctions, and two single-dot electrometers. The device is operated by applying inputs to the gates of the cell. The logic AND and OR operations are verified using the electrometer outputs. Theoretical simulations of the logic gate output characteristics are in excellent agreement with experiment.

Most of the matter in the Universe is not luminous, and can be observed only through its gravitational influence on the appearance of luminous matter. Weak gravitational lensing is a technique that uses the distortions of the images of distant galaxies as a tracer of dark matter: such distortions are induced as the light passes through large-scale distributions of dark matter in the foreground. The patterns of the induced distortions reflect the density of mass along the line of sight and its distribution, and the resulting ‘cosmic shear’ can be used to distinguish between alternative cosmologies. But previous attempts to measure this effect have been inconclusive. Here we report the detection of cosmic shear on angular scales of up to half a degree using 145,000 galaxies and along three separate lines of sight. We find that the dark matter is distributed in a manner consistent with either an open universe, or a flat universe that is dominated by a cosmological constant. Our results are inconsistent with the standard cold-dark-matter model.

Heterogeneous chip-to-chip interconnects with low loss and ultra-wide bandwidths have been demonstrated. Coplanar waveguide-based interconnects between GaAs and Si die have been fabricated and characterized and the results compared to expectations from full-wave electromagnetic simulation. Broadband transmission characteristics were obtained, with insertion losses below 0.3 dB at 100 GHz and below 0.8 dB at frequencies up to 220 GHz demonstrated experimentally. The measured return loss exceeded 11.5 dB at all frequencies up to 220 GHz. The interconnects offer low latency, with a measured group delay of 0.69 ps. The measured results are in good agreement with full-wave simulations, indicating that the measured results do not suffer from significant impairments compared to theoretical predictions. The demonstrated interconnects offer an alternative to conventional approaches to millimeter-wave circuit and system integration, by enabling the compact realization of circuits in the microwave, millimeter-wave, sub-millimeter-wave, and THz frequency regimes in heterogeneous device technologies with very low chip-to-chip insertion loss.

Summary Generally, in scanning electron microscopy (SEM) imaging, it is desirable that a high‐resolution image be composed mainly of those secondary electrons (SEs) generated by the primary electron beam, denoted SEI. However, in conventional SEM imaging, other, often unwanted, signal components consisting of backscattered electrons (BSEs), and their associated SEs, denoted SEII, are present; these signal components contribute a random background signal that degrades contrast, and therefore signal‐to‐noise ratio and resolution. Ideally, the highest resolution SEM image would consist only of the SEI component. In SEMs that use conventional pinhole lenses and their associated Everhart–Thornley detectors, the image is composed of several components, including SEI, SEII, and some BSE, depending on the geometry of the detector. Modern snorkel lens systems eliminate the BSEs, but not the SEIIs. We present a microfabricated diaphragm for minimizing the unwanted SEII signal components. We present evidence of improved imaging using a microlithographically generated pattern of Au, about 500 nm thick, that blocks most of the undesired signal components, leaving an image composed mostly of SEIs. We refer to this structure as a “spatial backscatter diaphragm.” SCANNING 35:1‐6, 2013. © 2012 Wiley Periodicals, Inc.

Future orbiting observatories will survey large areas of sky in order to constrain the physics of dark matter and dark energy using weak gravitational lensing and other methods. Lossy compression of the resultant data will improve the cost and feasibility of transmitting the images through the space communication network. We evaluate the consequences of the lossy compression algorithm of Bernstein et al. for the high-precision measurement of weak-lensing galaxy ellipticities. This square-root algorithm compresses each pixel independently, and the information discarded is, by construction, less than the Poisson error from photon shot noise. For simulated space-based images (without cosmic rays) digitized to the typical16 bits pixel-1 16     bits     pixe l - 1 , application of the lossy compression followed by imagewise lossless compression yields images with only2.4 bits pixel-1 2.4     bits     pixe l - 1 , a factor of 6.7 compression. We demonstrate that this compression introduces no bias in the sky background. The compression introduces a small amount of additional digitization noise to the images, and we demonstrate a corresponding small increase in ellipticity measurement noise. The ellipticity measurement method is biased by the addition of noise, so the additional digitization noise is expected to induce a multiplicative bias on the galaxies’ measured ellipticities. After correcting for this known noise-induced bias, we find a residual multiplicative ellipticity bias of m ≈ -4 × 10-4 m ≈ - 4 × 10 - 4 . This bias is small when compared with the many other issues that precision weak-lensing surveys must confront; furthermore, we expect it to be reduced further with better calibration of ellipticity measurement methods.