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oe1(光电查) - 科学论文

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  • Coherent Tabletop EUV Ptychography of Nanopatterns

    摘要： Coherent diffraction imaging (CDI) or lensless X-ray microscopy has become of great interest for high spatial resolution imaging of, e.g., nanostructures and biological specimens. There is no optics required in between an object and a detector, because the object can be fully recovered from its far-field diffraction pattern with an iterative phase retrieval algorithm. Hence, in principle, a sub-wavelength spatial resolution could be achieved in a high-numerical aperture configuration. With the advances of ultrafast laser technology, high photon flux tabletop Extreme Ultraviolet (EUV) sources based on the high-order harmonic generation (HHG) have become available to small-scale laboratories. In this study, we report on a newly established high photon flux and highly monochromatic 30 nm HHG beamline. Furthermore, we applied ptychography, a scanning CDI version, to probe a nearly periodic nanopattern with the tabletop EUV source. A wide-field view of about 15 × 15 μm was probed with a 2.5 μm?diameter illumination beam at 30 nm. From a set of hundreds of far-field diffraction patterns recorded for different adjacent positions of the object, both the object and the illumination beams were successfully reconstructed with the extended ptychographical iterative engine. By investigating the phase retrieval transfer function, a diffraction-limited resolution of reconstruction of about 32 nm is obtained.

    关键词： high-order harmonic generation,ptychography,lensless X-ray microscopy,Extreme Ultraviolet,Coherent diffraction imaging

    更新于2025-09-23 15:21:21

  • Photonic materials for high-temperature applications: Synthesis and characterization by X-ray ptychographic tomography

    摘要： Photonic materials for high-temperature applications need to withstand temperatures usually higher than 1000 ?C, whilst keeping their function. When exposed to high temperatures, such nanostructured materials are prone to detrimental morphological changes, however the structure evolution pathway of photonic materials and its correlation with the loss of material’s function is not yet fully understood. Here we use high-resolution ptychographic X-ray computed tomography (PXCT) and scanning electron microscopy (SEM) to investigate the structural changes in mullite inverse opal photonic crystals produced by a very-low-temperature (95 ?C) atomic layer deposition (ALD) super-cycle process. The 3D structural changes caused by the high-temperature exposure were quantified and associated with the distinct structural features of the ceramic photonic crystals. Other than observed in photonic crystals produced via powder colloidal suspensions or sol-gel infiltration, at high temperatures of 1400 ?C we detected a mass transport direction from the nano pores to the shells. We relate these different structure evolution pathways to the presence of hollow vertexes in our ALD-based inverse opal photonic crystals. Although the periodically ordered structure is distorted after sintering, the mullite inverse opal photonic crystal presents a photonic stopgap even after heat treatment at 1400 ?C for 100 h.

    关键词： Ptychography X-ray computed tomography,High-temperature applications,3D image analysis,Photonic materials,Low-temperature atomic layer deposition

    更新于2025-09-23 15:21:01

  • Correlations between lignin content and structural robustness in plants revealed by X-ray ptychography

    摘要： Lignin is a heterogeneous aromatic polymer responsible for cell wall stiffness and protection from pathogen attack. However, lignin represents a bottleneck to biomass degradation due to its recalcitrance related to the natural cell wall resistance to release sugars for fermentation or further processing. A biological approach involving genetics and molecular biology was used to disrupt lignin pathway synthesis and decrease lignin deposition. Here, we imaged three-dimensional fragments of the petioles of wild type and C4H lignin mutant Arabidopsis thaliana plants by synchrotron cryo-ptychography. the three-dimensional images revealed the heterogeneity of vessels, parenchyma, and fibre cell wall morphologies, highlighting the relation between disturbed lignin deposition and vessel implosion (cell collapsing and obstruction of water flow). We introduce a new parameter to accurately define cell implosion conditions in plants, and we demonstrate how cryo-ptychographic X-ray computed tomography (cryo-PXCT) provides new insights for plant imaging in three dimensions to understand physiological processes.

    关键词： lignin,structural robustness,X-ray ptychography,cryo-PXCT,plants,Arabidopsis thaliana

    更新于2025-09-23 15:19:57

  • [IEEE 2018 IEEE International Conference on Automation/XXIII Congress of the Chilean Association of Automatic Control (ICA-ACCA) - Concepcion, Chile (2018.10.17-2018.10.19)] 2018 IEEE International Conference on Automation/XXIII Congress of the Chilean Association of Automatic Control (ICA-ACCA) - Low-Cost High Resolution Microscopy based on Fourier Ptychography

    摘要： We present an advanced low-cost computational microscope based on simple components such as a cheap objective lens, a LED illumination matrix and 3D-printed parts. By implementing the Fourier Ptychographic Microscopy (FPM) technique onto a raspberry PI, we are able to acquire and synthetically produce images with wide field of view and high resolution. We present preliminary results, with the aim that at the end of this project, a low-cost kit will be presented to the community with assembly diagrams, 3D models and the FPM algorithms developed as a fully integrated system, so that it can be used and configured with relative simplicity such as in schools.

    关键词： computational imaging,phase retrieval,microscopy,Fourier ptychography

    更新于2025-09-19 17:15:36

  • [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) - Common Pulse Retrieval Algorithm: A Fast and Universal Method to Retrieve Ultrashort Pulses

    摘要： Measuring the temporal shape of ultrashort laser pulses is an important standard task in ultrafast optics. A multitude of methods has been devised for that purpose [1]. However, in many cases a specific, iterative algorithm has to be applied to retrieve the pulse shape from the measurement. In this work we present a common pulse retrieval algorithm (COPRA) that can be universally applied to such pulse measurement methods and compares favorably in terms of speed and accuracy to existing approaches [2]. For example, COPRA can be applied to the well-established frequency-resolved optical gating (FROG) [3], as well as, more recent techniques, such as dispersion scan (d-scan) [4] or time-domain ptychography (TDP) [5] (see Fig. 1). Generally, it is designed for a broad class of measurements where sets of pulse spectra after a nonlinear process such as second-harmonic generation (SHG) or third-harmonic generation (THG) are measured. Specifically, the measurement process has to be tunable by some parameter δ that forms the second measurement dimension. We call this class of measurements parametrized nonlinear process spectra (PNPS). COPRA now finds the pulse spectrum ?E(ω) that matches best to a PNPS measurement T meas(ω, δ ) in the least-squares sense. It does so in two stages: first the local iteration subsequently optimizes ?E(ω) with respect to single spectra, then the global iteration optimizes ?E(ω) with respect to the entire measurement. COPRA usually finds a least-squares solution to the pulse retrieval problem within a few hundreds iterations, i.e., within few tens of seconds on a standard workstation for usual measurement dimensions. This compares very favorably to existing approaches. Additionally, the retrieved pulses are more robust in the presence of Gaussian measurement noise than those retrieved by generalized projections or ptychography. Many existing pulse measurement schemes can directly benefit from COPRA for more robust and faster retrieval. Also, the framework of PNPS measurements may allow to gain more insight on fundamental questions of pulse measurement, will make measurement schemes more comparable and may lead to new and improved methods.

    关键词： time-domain ptychography,pulse retrieval,frequency-resolved optical gating,dispersion scan,ultrashort pulses

    更新于2025-09-12 10:27:22

  • Correlative 3D x-ray fluorescence and ptychographic tomography of frozen-hydrated green algae

    摘要： Accurate knowledge of elemental distributions within biological organisms is critical for understanding their cellular roles. The ability to couple this knowledge with overall cellular architecture in three dimensions (3D) deepens our understanding of cellular chemistry. Using a whole, frozen-hydrated Chlamydomonas reinhardtii cell as an example, we report the development of 3D correlative microscopy through a combination of simultaneous cryogenic x-ray ptychography and x-ray fluorescence microscopy. By taking advantage of a recently developed tomographic reconstruction algorithm, termed GENeralized Fourier Iterative REconstruction (GENFIRE), we produce high-quality 3D maps of the unlabeled alga’s cellular ultrastructure and elemental distributions within the cell. We demonstrate GENFIRE’s ability to outperform conventional tomography algorithms and to further improve the reconstruction quality by refining the experimentally intended tomographic angles. As this method continues to advance with brighter coherent light sources and more efficient data handling, we expect correlative 3D x-ray fluorescence and ptychographic tomography to be a powerful tool for probing a wide range of frozen-hydrated biological specimens, ranging from small prokaryotes such as bacteria, algae, and parasites to large eukaryotes such as mammalian cells, with applications that include understanding cellular responses to environmental stimuli and cell-to-cell interactions.

    关键词： GENFIRE,x-ray fluorescence microscopy,frozen-hydrated biological specimens,3D correlative microscopy,x-ray ptychography

    更新于2025-09-10 09:29:36

  • [IEEE 2018 New York Scientific Data Summit (NYSDS) - New York, NY, USA (2018.8.6-2018.8.8)] 2018 New York Scientific Data Summit (NYSDS) - High-Performance Multi-Mode Ptychography Reconstruction on Distributed GPUs

    摘要： Ptychography is an emerging imaging technique that is able to provide wavelength-limited spatial resolution from specimen with extended lateral dimensions. As a scanning microscopy method, a typical two-dimensional image requires a number of data frames. As a diffraction-based imaging technique, the real-space image has to be recovered through iterative reconstruction algorithms. Due to these two inherent aspects, a ptychographic reconstruction is generally a computation-intensive and time-consuming process, which limits the throughput of this method. We report an accelerated version of the multi-mode difference map algorithm for ptychography reconstruction using multiple distributed GPUs. This approach leverages available scienti?c computing packages in Python, including mpi4py and PyCUDA, with the core computation functions implemented in CUDA C. We ?nd that interestingly even with MPI collective communications, the weak scaling in the number of GPU nodes can still remain nearly constant. Most importantly, for realistic diffraction measurements, we observe a speedup ranging from a factor of 10 to 103 depending on the data size, which reduces the reconstruction time remarkably from hours to typically about 1 minute and is thus critical for real-time data processing and visualization.

    关键词： MPI,Python,CUDA,GPU,X-ray ptychography

    更新于2025-09-10 09:29:36

  • High-capacity encryption system based on single-shot-ptychography encoding and QR code

    摘要： We proposed a high-capacity optical encryption system based on single-shot-ptychography encoding (SPE) technique and quick response (QR) code. Two QR codes are utilized as date containers, one of which is encoded into random binary images (one is encoded image, another one is key) through visual cryptography (VC). Finally, the encoded images are encrypted by single-shot-ptychography encoding technology. It increases the variety of system-keys and overcomes the disadvantages of encrypting only binary images in SPE encoding systems. The security of the proposed system is mainly supported by VC extension encoding. The result of recovery does not have any distortion compared to the original plaintext. Simulation results show that this system has large-capacity information storage, powerful error correction capability, higher security and robustness.

    关键词： QR code,visual cryptography,single-shot-ptychography

    更新于2025-09-09 09:28:46

  • Three-Dimensional Imaging of Phase Ordering in an Fe-Al Alloy by Bragg Ptychography

    摘要： We show three-dimensional images of phase ordering in a Fe55Al45 alloy obtained by coherent x-ray diffraction Bragg ptychography. Fe-Al alloys display ordered phases where the atoms organize on sublattices resulting in the emergence of otherwise forbidden superlattice reflections. The degeneracy of the ordering results in antiphase domain boundaries that, in addition to the general lattice strain, provide phase shifts of the diffracted beam depending on the reflection. The reconstructed phase images can be separated into components originating from B2 phase domains and lattice strain by performing Bragg ptychography on both the (002) fundamental and the (001) superlattice reflections.

    关键词： lattice strain,three-dimensional imaging,antiphase domain boundaries,Fe-Al alloy,Bragg ptychography,phase ordering

    更新于2025-09-04 15:30:14

  • [IEEE 2018 IEEE International Conference on Computational Photography (ICCP) - Pittsburgh, PA (2018.5.4-2018.5.6)] 2018 IEEE International Conference on Computational Photography (ICCP) - ADP: Automatic differentiation ptychography

    摘要： Ptychography is an imaging technique which aims to recover the complex-valued exit wavefront of an object from a set of its diffraction pattern magnitudes. Ptychography is one of the most popular techniques for sub-30 nanometer imaging as it does not suffer from the limitations of typical lens based imaging techniques. The object can be reconstructed from the captured diffraction patterns using iterative phase retrieval algorithms. Over time many algorithms have been proposed for iterative reconstruction of the object based on manually derived update rules. In this paper, we adapt automatic differentiation framework to solve practical and complex ptychographic phase retrieval problems and demonstrate its advantages in terms of speed, accuracy, adaptability and generalizability across different scanning techniques.

    关键词： Imaging Technique,Ptychography,Automatic Differentiation,Phase Retrieval,Sub-30 Nanometer Imaging

    更新于2025-09-04 15:30:14