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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) - Inverse Photonic Design of Functional Elements That Focus Bloch Surface Waves
摘要： Bloch surface waves (BSWs) are surface states excited at the interface between a one-dimensional dielectric photonic crystal (1D-PC) and some ambient material. They are promising alternatives to propagating surface plasmon polaritons thanks to their much longer propagation lengths (up to thousand times the wavelength) that is not limited by absorption and the opportunity to excite them in both polarizations. They are currently considered for multiple applications in integrated optical systems or for sensing devices [1]. To control the propagation of BSWs, a structured functional layer is deposited on top of the 1D-PC. It consists of a thin dielectric layer with a desired shape that controls locally the dispersion relation of the BSW. This allows to implement, in general, optical elements with functions on demand. However, a severe limitation is the finite index contrast to be induced with the functional layer. For typical combinations of material and geometries, an index contrast only in the order of ~ 0.1 is achieved. This is insufficient to tightly focus a BSW with elements perceived by a rational design approach, e.g. with lens-like elements [2]. To solve this problem, we apply here methods developed in the context of computational photonic material design to perceive functional elements that focus BSWs highly efficiently [3]. We basically aim to solve the inverse problem. Computationally, we rely on a finite-difference frequency method as the Maxwell solver. To identify suitable structures, we discretize a finite spatial domain (typically in the order of 40μm x 10μm) where each pixel either is or is not covered by the functional layer. By systematically flipping each pixel, we can optimize structures that can focus the BSW into a predefined spatial domain. For a spatial domain directly behind the element, the BSW can be focused even below half its wavelength (a selected example is shown in Fig. 1a). To verify the findings, we fabricated the respective structures and measured the optical near-fields above them (a selected example is shown in Fig. 1b). The comparison between the simulation and the measurement shows an impressive agreement and allows to verify the ability to tightly focus the BSWs (Fig. 1c). This work introduces a new computational framework to design functional elements that can be used to control the propagation of BSWs and verifies it experimentally. Our approach is suitable for other material platforms where the limited index contrast is an obstacle to control the propagation of some waves. The elements we have studied can find immediate application in lab-on-chip systems where tightly focused BSWs interact with materials carried in fluidic channels to perform spectroscopic measurements.
关键词： functional elements,Bloch surface waves,photonic design,focusing,computational framework
更新于2025-09-23 15:19:57
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Metallic Nanomaterials (Part A) || 5. Synthesis and characterization of size-controlled atomically precise gold clusters
摘要： In this article, synthetic strategies and characterization methodologies of atomically precise gold clusters have been summarized. The typical and effective synthetic strategies including a systematic “size-focusing” methodology has been developed for attaining atomically precise gold clusters with size control. Another universal synthetic methodology is ligand exchange-induced size/structure transformation (LEIST) based on from one stable size to another. These two methodologies have largely expanded the “universe” of atomically precise gold clusters. Elite of typical synthetic case studies of ligand protected gold clusters are presented. Important characterization techniques of these atomically precise gold clusters also are included. The identification and characterization of gold clusters have been achieved in terms of nuclearity (size), molecular formulation, and geometrical structures by the combination of these techniques. The determination of gold cluster structure based on single crystals is of paramount importance in understanding the relationship of structure–property. The criterion and selection of these typical gold clusters are all “strictly” atomically precise that all have been determined ubiquitously by single crystal diffraction. These related crystallographic data are retrieved from Cambridge Crystallographic Data Centre (CCDC) up to 30th November 2017. Meanwhile, the cutting edge and other important characterization methodologies including electron diffraction (ED), extended X-ray absorption fine structure (EXFAS), and synchrotron sources are briefly reviewed. The new techniques hold the promise of pushing the limits of crystallization of gold clusters. This article is not just an exhaustive and up to date review, generally summarized synthetic strategies, but also a practical guide regarding gold cluster synthesis. We called it a “Cookbook” of ligand protected gold clusters, including synthetic recipes and characterization details.
关键词： alkyne,ligand exchange-induced size/structure transformation,phosphine,“size-focusing” methodology,size-controlled synthesis,thiolate,gold cluster
更新于2025-09-23 15:19:57
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Performance of assembled X-ray optics consisted of a polycapillary X-ray optics and a monocapillary X-ray optics for micro X-ray fluorescence spectrometry
摘要： A micro X-ray fluorescence (μ-XRF) spectrometry instrument based on an assembled X-ray optics was constructed in the laboratory. The assembled X-ray optics consisted of a polycapillary slightly focusing X-ray lens and a tapered monocapillary X-ray lens (TMXRL). The output X-ray beam of the polycapillary slightly focusing X-ray lens was focused again by the TMXRL. A TMXRL with output aperture of 12.01 μm was drawn by a nested glass tube. To evaluate the performance of the instrument, a performance comparison between different capillary X-ray optics was conducted. The intensity of the Fe Kα from an iron plate was used to indicate the analysis efficiency of the μ-XRF instrument. The relative gain of the instrument was corrected by comparing the intensity per unit area for a pinhole aperture. Compared with TMXRL single used, the assembled X-ray optics also had a micro focal spot. Furthermore, the relative gain of the assembled X-ray optics and the intensity of the Fe Kα from the iron plate obtained by the assembled X-ray optics were approximately 5 times those of the TMXRL single used. This highly intense micro X-ray beam with several diameters obtained by the assembled X-ray optics will be useful for μ-XRF analysis.
关键词： Capillary X-ray optics,Micro X-ray focusing,Micro X-ray fluorescence,Laboratory X-ray source
更新于2025-09-23 15:19:57
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[Laser Institute of America ICALEO?? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18a??22, 2015)] International Congress on Applications of Lasers & Electro-Optics - New generation of high power reflective focusing optics (HPRFO)
摘要： As the high power laser market continues to grow, so does the need for robust optical solutions that can withstand the inherently harsh environment of laser welding. EWI continues to push the design envelope for high power optics that are capable of withstanding 20 kW or more of laser power for extended periods of time. A second version of EWI’s high power reflective focusing optics, referred to as HPRFO2, incorporates a patented aero window for internal protection of critical components, improved process effluent protection, and a revised beam delivery path. Long focal lengths separate the critical optics from the harsh welding environment without compromising the focal spot size. The previously published results of version one of the HPRFO exhibited minimal focal shift, unmatched by commercially available optics. In this work a production hardened version was designed and tested. Key attributes, which proved successful in version one of the HPRFO, were incorporated in the new design along with changes resulting from lessons learned. Shallower fold angles (compared to original HPRFO) for the asymmetric aspheric mirrors, adaptable effluent management solutions and better thermal management were included in the new design. Initial testing of the HPRFO2 demonstrated promising results and robustness unrivaled by commercially available optics.
关键词： HPRFO,reflective focusing optics,high power laser,thermal management,aero window
更新于2025-09-23 15:19:57
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Self-focusing of multi-Gaussian laser beams in nonlinear optical media as a Keplera??s central force problem
摘要： In this paper self-focusing of multi-Gaussian laser beam in nonlinear optical media has been investigated theoretically. Saturation of the optical nonlinearity has been incorporated through cubic-quintic model. Moment theory approach in W.K.B approximation has been invoked to find the numerical solution of nonlinear wave equation for the field of incident laser beam. Particularly the dynamical evolutions of the beam width of the laser beam with distance of propagation have been investigated in detail. It has been shown that the self-focusing of the laser beam resembles to Kepler’s central force problem.
关键词： Potential well,Self focusing,Kepler’s central force problem,Multi Gaussian
更新于2025-09-23 15:19:57
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Polarization Controlled Dual Functional Reflective Planar Metalens in Near Infrared Regime
摘要： The metalens has been a hotspot in scienti?c communications in recent years. The polarization-controlled functional metalens is appealing in metalens investigation. We propose a metalens with dual functions that are controlled by polarization states. In the ?rst design, when applied with x- and y-polarized light, two focal spots with di?erent focal lengths are acquired, respectively. The proposed metalens performs well when illuminated with adjacent wavelengths. In the second design, the re?ected light is focused when applied with x-polarized light, and when applied with y-polarized light, the re?ected light is split into two oblique paths. We believe that the results will provide a new method in light manipulation.
关键词： splitting,focusing,dual functional-metalens,polarization controlling
更新于2025-09-23 15:19:57
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Role of magnetic field on self focusing of super-Gaussian laser beam under relativistic effect
摘要： Considering an external magnetic field along the direction of propagation of laser, the self focusing of a super-Gaussian laser beam is studied when it propagates through the plasma at relativistic intensities. We consider the cyclotron motion of the electrons and use the tensor form of the plasma dielectric constant obtained based on the direction of the external magnetic field. For completeness, relativistic mass effect is incorporated in both the plasma frequency and electron cyclotron frequency. Using appropriate conditions, an equation for the beam width parameter is derived and solved. The equilibrium beam radius for a self trapped laser beam is also derived. Self focusing is better when cyclotron effects are taken into account. At higher intensity and higher spot size of the laser beam, self focusing becomes better.
关键词： Super-Gaussian laser,Moment theory,Beam width parameter,Self focusing,Relativistic nonlinearity
更新于2025-09-23 15:19:57
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Omni-direction PERC solar cells harnessing periodic locally focused light incident through patterned PDMS encapsulation
摘要： Photovoltaic panels based on crystalline Si solar cells are the most widely utilized renewable source of electricity, and there has been a significant effort to produce panels with a higher energy conversion efficiency. Typically, these developments have focused on cell-level device modifications to restrict the recombination of photo-generated charge carriers, and concepts such as back surface field, passivated emitter and rear contact (PERC), interdigitated back contact, and heterojunction with intrinsic thin layer solar cells have been established. Here, we propose quasi-Fermi level control using periodic local focusing of incident light by encapsulation with polydimethylsiloxane to improve the performance of solar cells at the module-level; such improvements can complement cell-level enhancements. Locally focused incident light is used to modify the internal quasi-Fermi level of PERC solar cells owing to the localized photon distribution within the cell. Control of the local focusing conditions induces different quasi-Fermi levels, and therefore results in different efficiency changes. For example, central focusing between fingers enhances the current density with a reduced fill factor, whereas multiple local focusing enhances the fill factor rather than the current density. Here, these effects were explored for various angles of incidence, and the total electrical energy production was increased by 3.6% in comparison to a bare cell. This increase is significant as conventional ethylene vinyl acetate-based encapsulation reduces the efficiency as short-wavelength light is attenuated. However, this implies that additional module-scale studies are required to optimize local focusing methods and their synergy with device-level modifications to produce advanced photovoltaics.
关键词： quasi-Fermi level control,module-level enhancements,energy conversion efficiency,Photovoltaic panels,crystalline Si solar cells,local focusing,polydimethylsiloxane,PERC solar cells
更新于2025-09-23 15:19:57
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Electrochemical Coupled Analysis of a Micro Piezo-Driven Focusing Mechanism
摘要： In order to improve the response speed and output force of the camera focusing mechanism, the authors proposed a novelty micro focusing mechanism based on piezoelectric driving, which has the characteristics of rapid response, high precision positioning and large displacement focusing. In this paper, the operating principle of the proposed focusing mechanism is presented. Using the piezoelectric output characteristic, the movable tooth drive theory and the screw drive theory, the electromechanical coupling mechanical model and equations of the piezoelectric focusing mechanism are established. Through MATLAB simulation, the output characteristics of the piezoelectric focusing mechanism are calculated. The results indicate that the maximum thrust force of the lens and the maximum output torque of the movable tooth drive for the piezoelectric focusing mechanism are 562.5 N and 1.16 Nm, respectively. Furthermore, the driving voltage directly affects the output performance of the piezoelectric focusing mechanism. These results can be utilized both to optimize the dimensions and improve the overall performance of the piezo‐driven focusing mechanism.
关键词： focusing mechanism,piezo‐driven,numerical analysis,electrochemical coupled
更新于2025-09-23 15:19:57
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[IEEE 2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting - Boston, MA, USA (2018.7.8-2018.7.13)] 2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting - Millimeter-Wave Synthetic Aperture Focusing for Packaging Inspection System
摘要： Synthetic aperture focusing technique is proposed for developing a packaging inspection system. The SAF algorithm is reformulated. The SAF reformulation is tested for a package inspection application with finite element simulation data.
关键词： synthetic aperture radar,Synthetic aperture focusing,and inspection,sectional imaging,image reconstruction,Fourier optics
更新于2025-09-19 17:15:36