- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Visualization of different carrier concentrations in n-type-GaN semiconductors by phase-shifting electron holography with multiple electron biprisms
摘要： Phase-shifting electron holography (PS-EH) using a transmission electron microscope (TEM) was applied to visualize layers with different concentrations of carriers activated by Si (at dopant levels of 1019, 1018, 1017 and 1016 atoms cm?3) in n-type GaN semiconductors. To precisely measure the reconstructed phase pro?les in the GaN sample, three electron biprisms were used to obtain a series of high-contrast holograms without Fresnel fringes generated by a biprism ?lament, and a cryo-focused-ion-beam (cryo-FIB) was used to prepare a uniform TEM sample with less distortion in the wide ?eld of view. All layers in a 350-nm-thick TEM sample were distinguished with 1.8-nm spatial resolution and 0.02-rad phase-resolution, and variations of step width in the phase pro?le (corresponding to depletion width) at the interfaces between the layers were also measured. Thicknesses of the active and inactive layers at each dopant level were estimated from the observed phase pro?le and the simulation of theoretical band structure. Ratio of active-layer thickness to total thickness of the TEM sample signi?cantly decreased as dopant concentration decreased; thus, a thicker TEM sample is necessary to visualize lower carrier concentrations; for example, to distinguish layers with dopant concentrations of 1016 and 1015 atoms cm?3. It was estimated that sample thickness must be more than 700 nm to make it be possible to detect sub-layers by the combination of PS-EH and cryo-FIB.
关键词： phase-shifting electron holography,dopant pro?ling,carrier concentration,GaN,inactive layer,active layer
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - In Flow Manipulation and Characterization of Cancer Cells by Coherent Computational Microscopy
摘要： Liquid biopsy has shown remarkably promising in oncology for the early diagnosis of cancer through the detection of circulating biomarkers such as circulating tumor cells (CTCs). Recent evidences suggest that CTCs represent effective prognostic and predictive biomarkers to monitor/predict therapy efficacy in breast, colon and prostate cancers [1,2]. However, the frequency of CTCs in blood is approximately 1 to 10 cells per 10 mL of blood, which is as challenging as looking for a needle in a haystack. In microfluidics, Digital Holography (DH) has been shown to be a promising technique to characterize CTCs with the aim to detect them inside a heterogeneous liquid sample. DH is label-free, real-time and gives access to the complex amplitude of the object [3-6]. Thus, any classification approach based on the holographic signature can exploit a reach information content to take a decision. Moreover, the flexible refocusing capability of DH imaging allows to inspect an entire liquid volume with a single capture. This enables the high-throughput inspection of blood and other bodily fluids rapidly flowing inside microfluidic channels. In DH, the sample is probed from one single direction and the phase delay introduced by the sample in through transmission acts as a contrast agent. Hence, the optical thickness measurable by DH imaging is an integral information, i.e. the sum of all the contributions experienced by the coherent light during its passage through the sample. In order to decouple the refractive index from the physical thickness and to resolve its distribution along the optical axis, tomography exploits multiple recordings, probing the sample from different angles and combining the corresponding phase-contrast maps [7,8]. Various schemes have been proposed to minimize the number of sampling angles and to make the recording stage faster in order to match the requirements and time constraints imposed by real biological problems. Here we show the recent advances of in-flow holographic tomography, which exploits a controlled induced rotation of the sample inside the microfluidic channel to probe it from different view angles with no mechanical rotation of the source beam [8,9]. We introduce an effective algorithm to recover from the recorded phase maps the set of angles required as input of the optical projection tomography algorithm [7-9]. We show the application of holographic flow tomography to the characterization of different cancer cells [10], namely breast cancer cells, ovarian cancer cells and neuroblastoma. We also discuss different possibilities of Lab-on-a-Chip design and flow engineering that allow us to induce controlled rotations while maintaining the high-throughput nature of DH microscopy [9,11,12]. In the next future, the large amount of data obtainable by this approach will be used to train a neural network devoted to classify CTCs, distinguishing them from the other components of a blood stream.
关键词： liquid biopsy,cancer cells,microfluidics,circulating tumor cells,holographic tomography,Lab-on-a-Chip,digital holography
更新于2025-09-16 10:30:52
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Wirtinger holography for near-eye displays
摘要： Near-eye displays using holographic projection are emerging as an exciting display approach for virtual and augmented reality at high-resolution without complex optical setups D shifting optical complexity to computation. While precise phase modulation hardware is becoming available, phase retrieval algorithms are still in their infancy, and holographic display approaches resort to heuristic encoding methods or iterative methods relying on various relaxations. In this work, we depart from such existing approximations and solve the phase retrieval problem for a hologram of a scene at a single depth at a given time by revisiting complex Wirtinger derivatives. We also discuss extending our framework to render 3D volumetric scenes. Using Wirtinger derivatives allows us to pose the phase retrieval problem as a quadratic problem which can be minimized with first-order optimization methods. The proposed Wirtinger Holography is flexible and facilitates the use of different loss functions, including learned perceptual losses parametrized by deep neural networks, as well as stochastic optimization methods. We validate this framework by demonstrating holographic reconstructions with an order of magnitude lower error, both in simulation and on an experimental hardware prototype.
关键词： augmented reality,computer generated holography,near-eye display,vergence-accommodation conflict,computational displays,virtual reality
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Zhenjiang, China (2019.8.4-2019.8.8)] 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Imaging Analysis of Micro-milling Tool in the Process of Tool Setting Based on Digital Holography
摘要： In the process of ultra-precision machining, the tool-setting accuracy of the micro-milling tool is limited by the tool diameter. The accuracy of tool setting decreases with the decrease of tool diameter, which becomes an important factor for restricting the accuracy of ultra-precision machining. Based on the imaging principle of digital in-line holography, an efficient and non-contacted method for tool setting was proposed for improving the accuracy of tool setting. Aiming at the imaging problem of micro-milling tool, the evaluation function based on wavelet transform was introduced in the process of progressive search, so the optimal reconstructed image was accurately obtained through the autofocusing algorithm. Then the zero-order term and the conjugate image were eliminated via the self-snake diffusion. The tool contour was extracted by Sobel operator, and tool diameter was measured using different methods. Measurement results proved that holographic imaging can meet the requirements of in-position dynamic measurement for micro-milling tools, and also provided an important basis for the accuracy of tool setting.
关键词： tool setting,auto-focusing,digital holography
更新于2025-09-16 10:30:52
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Generation of Flat Top Surface Plasmon Polariton Beams by Near Field Holography
摘要： Controlling the shape and trajectory of the surface plasmon polariton (SPP) beams is the key to all SPP-based applications. In this paper, a novel plasmonic device that can generate in-plane ?at top SPP beams is designed by near ?eld holography. The relationship between the transverse pro?le intensity of the generated ?at top SPP beams and the structural parameters of the designed device is analyzed. The results of this paper can provide the possibility for further practical application utilizing ?at top SPP beams.
关键词： surface plasmonic polariton,near ?eld holography,?at top SPP beams
更新于2025-09-16 10:30:52
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[IEEE 2019 19th International Workshop on Junction Technology (IWJT) - Kyoto, Japan (2019.6.6-2019.6.7)] 2019 19th International Workshop on Junction Technology (IWJT) - Three-dimensional dopant imaging in semiconductor crystals using photoelectron holography with chemical state identification
摘要： Doping is an important technology for modern science. For example, to create a semiconductor device, a circuit is formed by controlling carriers by doping. It is important to search for appropriate conditions since the carrier emission from dopant differs depending on the doping conditions. The atomic arrangement around the dopant differs depending on the conditions. Therefore, it has been desired to observe the atomic arrangement around the dopant, but it has been difficult with conventional measurement methods. The resolution holography such as photoelectron atomic holography, x-ray fluorescence holography, neutron holography, which are methods that can measure the three-dimensional (3D) atomic arrangement of the dopant. Among them, photoelectron holography can measure the atomic structure of each dopant depending on the chemical state. We have built photoelectron holography apparatuses at BL25SU in SPring-8. We also developed a software platform 3D-AIR-IMAGE for data processing, simulation of photoelectron holograms, and 3D atomic image reconstruction.
关键词： photoelectron holography,doping,semiconductor,chemical state identification,3D atomic arrangement
更新于2025-09-16 10:30:52
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Photoelectron holography from multiple-return backscattering electron orbits
摘要： We theoretically investigate the photoelectron momentum distributions of a diatomic molecule in a linearly polarized two-color laser ?eld by solving the time-dependent Schr?dinger equation. An upward curvature interference pattern is found in the two-dimensional photoelectron momentum spectra. Resorting to a simple semiclassical analysis and the strong-?eld approximation theory, we show that the interference pattern corresponds to a holographic pattern from the second-return backscattering electron orbits and, furthermore, the underlying physics of the distinct observation of such interference pattern is revealed. The holographic patterns from the backscattering electron orbits with the different return times may encode the information of the target structure at different times after ionization.
关键词： strong-?eld approximation theory,backscattering electron orbits,time-dependent Schr?dinger equation,photoelectron holography
更新于2025-09-16 10:30:52
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Nonlinear Oscillatory Shear Tests in Viscoelastic Holography
摘要： We provide the first characterization of the nonlinear and time dependent rheologic response of viscoelastic bottom-up holographic models. More precisely, we perform oscillatory shear tests in holographic massive gravity theories with finite elastic response, focusing on the large amplitude oscillatory shear (LAOS) regime. The characterization of these systems is done using several techniques: (i) the Lissajous figures, (ii) the Fourier analysis of the stress signal, (iii) the Pipkin diagram and (iv) the dependence of the storage and loss moduli on the amplitude of the applied strain. We find substantial evidence for a strong strain stiffening mechanism, typical of hyperelastic materials such as rubbers and complex polymers. This indicates that the holographic models considered are not a good description for rigid metals, where strain stiffening is not commonly observed. Additionally, a crossover between a viscoelastic liquid regime at small graviton mass (compared to the temperature scale), and a viscoelastic solid regime at large values is observed. Finally, we discuss the relevance of our results for soft matter and for the understanding of the widely used homogeneous holographic models with broken translations.
关键词： LAOS regime,viscoelastic holography,strain stiffening,nonlinear oscillatory shear tests,viscoelastic materials
更新于2025-09-16 10:30:52
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[Institution of Engineering and Technology 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Lecce, Italy (23-25 May 2018)] 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Polarization digital holography for birefringence characterization of sperm cells
摘要： Birefringence in sperm heads depends on a very compact and organized structural normality. Additionally, when the acrosome reaction happens, due to a reorganization of the proteins, the birefringence occurs only in the post-acrosomal region. Thus, the polarization state of the semen is an interesting method to characterize their healthy state and to select reacted sperm cells. In this paper, a characterization of the birefringence pattern of sperm head by polarized digital holography microscopy is presented as a label free technique.
关键词： Digital holography,Sperm selection,Digital morphology,Sperm texture,Birefringence
更新于2025-09-16 10:30:52
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When the Image Takes over the Real: Holography and Its Potential within Acts of Visual Documentation
摘要： In Camera Lucida, Roland Barthes discusses the capacity of the photographic image to represent “?at death”. Documentation of an event, happening, or time is traditionally reliant on the photographic to determine its ephemeral existence and to secure its legacy within history. However, the traditional photographic document is often unsuitable to capture the real essence and experience of the artwork in situ. The hologram, with its potential to o?er a three-dimensional viewpoint, suggests a desirable solution. However, there are issues concerning how this type of photographic document successfully functions within an art context. Attitudes to methods necessary for artistic production, and holography’s place within the process, are responsible for this problem. The seductive qualities of holography may be attributable to any failure that ensues, but, if used precisely, the process can be e?ective to create a document for ephemeral art. The failures and successes of the hologram to be reliable as a document of experience are discussed in this article, together with a suggestion of how it might undergo a transformation and reactivation to become an artwork itself.
关键词： documentation,Bartram,document,hologram,holography,artwork,ephemeral
更新于2025-09-16 10:30:52