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https://www.readbyqxmd.com/read/28615684/flat-terahertz-reflective-focusing-metasurface-with-scanning-ability
#1
Huan Yi, Shi-Wei Qu, Bao-Jie Chen, Xue Bai, Kung Bo Ng, Chi Hou Chan
The ability to manipulate the propagation properties of electromagnetic waves, e.g., divergence, focusing, holography or deflection, is very significant in terahertz applications. Metasurfaces with flat structures are attractive for achieving such manipulations in terahertz band, as they feature low profile, lightweight, and ease of design and installation. Several types of terahertz reflective or transmitting metasurfaces with focusing function have been implemented recently, but none of them can provide scanning ability with controllable focus...
June 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28589931/inhomogeneous-spatial-distribution-of-the-magnetic-transition-in-an-iron-rhodium-thin-film
#2
C Gatel, B Warot-Fonrose, N Biziere, L A Rodríguez, D Reyes, R Cours, M Castiella, M J Casanove
Monitoring a magnetic state using thermal or electrical activation is mandatory for the development of new magnetic devices, for instance in heat or electrically assisted magnetic recording or room-temperature memory resistor. Compounds such as FeRh, which undergoes a magnetic transition from an antiferromagnetic state to a ferromagnetic state around 100 °C, are thus highly desirable. However, the mechanisms involved in the transition are still under debate. Here we use in situ heating and cooling electron holography to quantitatively map at the nanometre scale the magnetization of a cross-sectional FeRh thin film through the antiferromagnetic-ferromagnetic transition...
June 7, 2017: Nature Communications
https://www.readbyqxmd.com/read/28584259/complex-beam-shaping-based-on-an-equivalent-q-plate-system-and-analysis-of-its-properties-using-digital-holography-polarization-imaging
#3
Ching-Han Yang, Andy Ying-Guey Fuh
In this study, we generate various complex beams carrying angular momentum (AM) by using a programmable beam shaping system to mimic typical q-plates. When a circularly polarized wave is incident onto the system, the emerging beam reverses its spin handedness and obtains a spatial phase factor. This phase factor can be engineered by designing a computer-generated hologram (CGH) and applying it to a spatial light modulator (SLM) to produce a beam with controllable spatially distributed orbital angular momentum (OAM) density...
June 5, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28581771/surface-states-in-holographic-weyl-semimetals
#4
Markus Heinrich, Amadeo Jiménez-Alba, Sebastian Moeckel, Martin Ammon
We study the surface states of a strongly coupled Weyl semimetal within holography. By explicit numerical computation of an inhomogeneous holographic Weyl semimetal, we observe the appearance of an electric current restricted to the surface in the presence of an electric chemical potential. The integrated current is universal in the sense that it only depends on the topology of the phases showing that the bulk-boundary correspondence holds even at strong coupling. The implications of this result are subtle and may shed some light on anomalous transport at weak coupling...
May 19, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28578832/a-biophysical-approach-to-quantify-skeletal-stem-cells-trans-differentiation-as-a-model-for-the-study-of-osteoporosis
#5
L Petecchia, F Viti, F Sbrana, M Vassalli, P Gavazzo
The stroma of human bone marrow contains a population of skeletal stem cells (hBM-MSC) which are common ancestors, among the others, of osteoblasts and adipocytes. It has been proposed that the imbalance between hBM-MSC osteogenesis and adipogenesis, which naturally accompanies bone marrow senescence, may contribute to the development of bone-associated diseases, like osteoporosis. The possibility to reproduce this mechanism in vitro has been demonstrated, providing a good model to disclose the details of the complex bone-fat generation homeostasis...
May 26, 2017: Biophysical Chemistry
https://www.readbyqxmd.com/read/28524674/holography-of-wi-fi-radiation
#6
Philipp M Holl, Friedemann Reinhard
Wireless data transmission systems such as wi-fi or Bluetooth emit coherent light-electromagnetic waves with a precisely known amplitude and phase. Propagating in space, this radiation forms a hologram-a two-dimensional wave front encoding a three-dimensional view of all objects traversed by the light beam. Here we demonstrate a scheme to record this hologram in a phase-coherent fashion across a meter-sized imaging region. We recover three-dimensional views of objects and emitters by feeding the resulting data into digital reconstruction algorithms...
May 5, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28523281/imaging-membrane-potential-changes-from-dendritic-spines-using-computer-generated-holography
#7
Dimitrii Tanese, Ju-Yun Weng, Valeria Zampini, Vincent De Sars, Marco Canepari, Balazs Rozsa, Valentina Emiliani, Dejan Zecevic
Electrical properties of neuronal processes are extraordinarily complex, dynamic, and, in the general case, impossible to predict in the absence of detailed measurements. To obtain such a measurement one would, ideally, like to be able to monitor electrical subthreshold events as they travel from synapses on distal dendrites and summate at particular locations to initiate action potentials. It is now possible to carry out these measurements at the scale of individual dendritic spines using voltage imaging. In these measurements, the voltage-sensitive probes can be thought of as transmembrane voltmeters with a linear scale, which directly monitor electrical signals...
July 2017: Neurophotonics
https://www.readbyqxmd.com/read/28516906/nanometric-holograms-based-on-a-topological-insulator-material
#8
Zengji Yue, Gaolei Xue, Juan Liu, Yongtian Wang, Min Gu
Holography has extremely extensive applications in conventional optical instruments spanning optical microscopy and imaging, three-dimensional displays and metrology. To integrate holography with modern low-dimensional electronic devices, holograms need to be thinned to a nanometric scale. However, to keep a pronounced phase shift modulation, the thickness of holograms has been generally limited to the optical wavelength scale, which hinders their integration with ultrathin electronic devices. Here, we break this limit and achieve 60 nm holograms using a topological insulator material...
May 18, 2017: Nature Communications
https://www.readbyqxmd.com/read/28490745/a-nanofabricated-monolithic-path-separated-electron-interferometer
#9
Akshay Agarwal, Chung-Soo Kim, Richard Hobbs, Dirk van Dyck, Karl K Berggren
Progress in nanofabrication technology has enabled the development of numerous electron optic elements for enhancing image contrast and manipulating electron wave functions. Here, we describe a modular, self-aligned, amplitude-division electron interferometer in a conventional transmission electron microscope. The interferometer consists of two 45-nm-thick silicon layers separated by 20 μm. This interferometer is fabricated from a single-crystal silicon cantilever on a transmission electron microscope grid by gallium focused-ion-beam milling...
May 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28489065/sound-source-localization-using-non-conformal-surface-sound-field-transformation-based-on-spherical-harmonic-wave-decomposition
#10
Lanyue Zhang, Dandan Ding, Desen Yang, Jia Wang, Jie Shi
Spherical microphone arrays have been paid increasing attention for their ability to locate a sound source with arbitrary incident angle in three-dimensional space. Low-frequency sound sources are usually located by using spherical near-field acoustic holography. The reconstruction surface and holography surface are conformal surfaces in the conventional sound field transformation based on generalized Fourier transform. When the sound source is on the cylindrical surface, it is difficult to locate by using spherical surface conformal transform...
May 10, 2017: Sensors
https://www.readbyqxmd.com/read/28482229/detecting-dynamic-responses-of-materials-and-devices-under-an-alternating-electric-potential-by-phase-locked-transmission-electron-microscopy
#11
Kentaro Soma, Stan Konings, Ryotaro Aso, Naoto Kamiuchi, Genki Kobayashi, Hideto Yoshida, Seiji Takeda
An apparatus is developed for transmission electron microscopy (TEM) to acquire image and spectral data, such as TEM images, electron holograms, and electron energy loss spectra, synchronized with the measurement of the dynamic response of a specimen under an applied alternating current (AC) electric potential (voltage, denoted VAC). From a VAC of frequency f, a shutter pulse signal is generated to open and close a pre-specimen shutter in a base TEM apparatus. A pulse is generated per VAC cycle from the targeted phase Φ to Φ +∆Φ with phase width ∆Φ (∆Φ <2π)...
April 29, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28463316/multiwavelength-off-axis-digital-holography-with-an-angle-of-more-than-40%C3%A2-%C3%A2-degrees-and-no-beam-combiner-to-generate-interference-light
#12
Tatsuki Tahara, Yasuhiko Arai
We propose single-shot multiwavelength digital holography with an extremely large incident angle and show the digital recording of multiple object waves at multiple wavelengths with an angle of more than 40 degrees and no beam combiner to generate interference light. Both the avoidance of the crosstalk between the object waves at different wavelengths and the space-bandwidth extension are simultaneously achieved with a single-shot exposure of a monochromatic image sensor and a reference beam even when the wavelength difference between the object waves is small...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28463315/self-calibration-for-lensless-color-microscopy
#13
Olivier Flasseur, Corinne Fournier, Nicolas Verrier, Loïc Denis, Frédéric Jolivet, Anthony Cazier, Thierry Lépine
Lensless color microscopy (also called in-line digital color holography) is a recent quantitative 3D imaging method used in several areas including biomedical imaging and microfluidics. By targeting cost-effective and compact designs, the wavelength of the low-end sources used is known only imprecisely, in particular because of their dependence on temperature and power supply voltage. This imprecision is the source of biases during the reconstruction step. An additional source of error is the crosstalk phenomenon, i...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28463312/observation-of-dehydration-dynamics-in-biological-tissues-with-terahertz-digital-holography-invited
#14
Lihan Guo, Xinke Wang, Peng Han, Wenfeng Sun, Shengfei Feng, Jiasheng Ye, Yan Zhang
A terahertz (THz) digital holographic imaging system is utilized to investigate natural dehydration processes in three types of biological tissues, including cattle, mutton, and pork. An image reconstruction algorithm is applied to remove the diffraction influence of THz waves and further improve clarity of THz images. From THz images of different biological specimens, distinctive water content as well as dehydration features of adipose and muscle tissues are precisely distinguished. By analyzing THz absorption spectra of these samples, temporal evolution characteristics of the absorbances for adipose and muscle tissues are described and compared in detail...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28463311/quality-assessment-of-refocus-criteria-for-particle-imaging-in-digital-off-axis-holography
#15
Soumaya Kara Mohammed, Larbi Bouamama, Derradji Bahloul, Pascal Picart
This paper proposes a quality assessment of focusing criteria for imaging in digital off-axis holography. In the literature, several refocus criteria have been proposed in the past to get the best refocus distance in digital holography. As a general rule, the best focusing plane is determined by the reconstruction distance for which the criterion function presents a maximum or a minimum. To evaluate the robustness of these criteria, 13 criteria are compared with application on both amplitude and phase objects from off-axis holographic data...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28463310/fast-autofocusing-in-digital-holography-using-the-magnitude-differential
#16
Meng Lyu, Caojin Yuan, Dayan Li, Guohai Situ
Typical methods of automatic estimation of focusing in digital holography calculate every single reconstructed frame to get a critical function and then ascertain the focal plane by finding the extreme value of that function. Here, we propose a digital holographic autofocusing method that computes the focused distance using the first longitudinal difference of the magnitude of the reconstructed image. We demonstrate the proposed method with both numerical simulations and optical experiments of amplitude-contrast and phase-contrast objects...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28463305/optical-defocus-noise-suppressing-by-using-a-pinhole-polarizer-in-fresnel-incoherent-correlation-holography
#17
Ki-Hong Choi, Junkyu Yim, Sung-Wook Min
We propose the method that suppresses the defocus noise optically in the Fresnel incoherent correlation holographic system using a pinhole-polarizer (PP), which is made by punching a pinhole on the linear polarizer. The system configuration of this suggestion is based on the original system with optical-sectioning capability, which is realized by presenting the phase-pinhole on the phase-only spatial light modulator. In our system, the phase-pinhole is replaced with a PP. The replaced component is no longer programmable yet provides an affordable, simple, and light-efficient system configuration...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28463302/co-axis-digital-holography-based-on-sinusoidal-phase-modulation-using-generalized-lock-in-detection
#18
Yunlong Zhu, Julien Vaillant, Manuel François, Guillaume Montay, Aurélien Bruyant
Sinusoidal phase modulating (SPM) interferometers are used to precisely measure complex light fields with simple interferometric setups. Recently, a generalized lock-in technique has been proposed for optimizing the signal extraction in phase-modulated interferometers. This article shows its applicability in digital holography as well as digital holographic interferometry. A compact homemade setup based on the Michelson interferometer was used to observe the scattering sample surface with a spatial resolution of 32 LP/mm; out-of-plane rotation was measured with a theoretical detection limit of 0...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28463301/self-interference-compressive-digital-holography-with-improved-axial-resolution-and-signal-to-noise-ratio
#19
Tianlong Man, Yuhong Wan, Fan Wu, Dayong Wang
Fresnel incoherent correlation holography (FINCH) was proposed to break the barrier of spatial incoherent digital holographic imaging and show the potential of super-resolution imaging preferences. We developed FINCH as a compressive sensing modality and reconstruction procedure as an inverse problem in order to realize 3D tomographic imaging. Improved axial resolution is obtained via compressive reconstruction. Reconstruction guarantees and accuracy of the proposed method are discussed. Compared with the real-valued signal operation, the signal-to-noise ratio of the results is increased when reconstructing from the complex-valued hologram obtained from the FINCH system...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28463300/speeding-up-image-quality-improvement-in-random-phase-free-holograms-using-ringing-artifact-characteristics
#20
Yuki Nagahama, Tomoyoshi Shimobaba, Takashi Kakue, Nobuyuki Masuda, Tomoyoshi Ito
A holographic projector utilizes holography techniques. However, there are several barriers to realizing holographic projections. One is deterioration of hologram image quality caused by speckle noise and ringing artifacts. The combination of the random phase-free method and the Gerchberg-Saxton (GS) algorithm has improved the image quality of holograms. However, the GS algorithm requires significant computation time. We propose faster methods for image quality improvement of random phase-free holograms using the characteristics of ringing artifacts...
May 1, 2017: Applied Optics
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