5 research outputs found
Deep learning–based vortex decomposition and switching based on fiber vector eigenmodes
Structured optical fields, such as cylindrical vector (CV) and orbital angular momentum (OAM) modes, have attracted considerable attention due to their polarization singularities and helical phase wavefront structure. However, one of the most critical challenges is still the intelligent generation or precise control of these modes. Here, we demonstrate the first simulation and experimental realization of decomposing the CV and OAM modes by reconstructing the multi-view images of projected intensity distribution. Assisted by the deep learning–based stochastic parallel gradient descent (SPGD) algorithm, the modal coefficients and optical field distributions can be retrieved in 1.32 s within an average error of 0.416 % showing high efficiency and accuracy. Especially, the interference pattern and quarter-wave plate are exploited to confirm the phase and distinguish elliptical or circular polarization direction, respectively. The generated donut modes are experimentally decomposed in the CV and OAM modes, where purity of CV modes reaches 99.5 %. Finally, fast switching vortex modes is achieved by electrically driving the polarization controller to deliver diverse CV modes. Our findings may provide a convenient way to characterize and deepen the understanding of CV or OAM modes in view of modal proportions, which is expected of latent applied value on information coding and quantum computation
Ordered Intermetallic Nanoparticles with High Catalytic Activity Prepared by an Electrochemically Induced Phase Transformation
The
synthesis of alloys with long range atomic scale ordering (ordered intermetallics)
is an emerging field of nanochemistry. Ordered intermetallic nanoparticles are
useful for a wide variety of applications such as catalysis, superconductors,
and magnetic devices. However, the preparation of nanostructured ordered
intermetallics is challenging in comparison to disordered alloys, hindering
progress in materials development. We report a process for converting
colloidally synthesized ordered intermetallic PdBi2 to ordered
intermetallic Pd3Bi nanoparticles under ambient conditions by an
electrochemically induced phase transition. The low melting point of PdBi2
corresponds to low vacancy formation energies which enables the facile removal
of the Bi from the surface, while simultaneously enabling interdiffusion of the
constituent atoms via a vacancy diffusion mechanism under ambient conditions.
The resulting phase-converted ordered intermetallic Pd3Bi exhibits
11x and 3.5x higher mass activty and high methanol tolerance for the oxygen
reduction reaction compared to Pt/C and Pd/C, respectively,which is the highest
reported for a Pd-based catalyst, to the best of our knowledge. These results
establish a key development in the synthesis of noble metal rich ordered
intermetallic phases with high catalytic activity, and sets forth guidelines
for the design of ordered intermetallic compounds under ambient conditions.
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Ultrathin quasi-2D amorphous carbon dielectric prepared from solution precursor for nanoelectronics
Abstract Materials keeping thickness in atomic scale but extending primarily in lateral dimensions offer properties attractive for many emerging applications. However, compared to crystalline counterparts, synthesis of atomically thin films in the highly disordered amorphous form, which avoids nonuniformity and defects associated with grain boundaries, is challenging due to their metastable nature. Here we present a scalable and solution-based strategy to prepare large-area, freestanding quasi-2D amorphous carbon nanomembranes with predominant sp2 bonding and thickness down to 1–2 atomic layers, from coal-derived carbon dots as precursors. These atomically thin amorphous carbon films are mechanically strong with modulus of 400 ± 100 GPa and demonstrate robust dielectric properties with high dielectric strength above 20 MV cm−1 and low leakage current density below 10−4 A cm−2 through a scaled thickness of three-atomic layers. They can be implemented as solution-deposited ultrathin gate dielectrics in transistors or ion-transport media in memristors, enabling exceptional device performance and spatiotemporal uniformity