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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - The Autoconvolution Method Use for Positioning Photonic Crystal Fibers
摘要： In this paper, the autoconvolution method was investigated to determine the position of the longitudinal axis of the photonic crystal fiber and to determine the center of the mode field in the cross section. Knowing the center of the PCF mode field, one can determine the cross section in which the diameter of the mode field will be maximal. This allows a more precise positioning of two identical PCF during connection. The proposed method allows improving the quality of the positioning of the PCF by transverse, angular, longitudinal displacements, and also by the mutual angle of rotation of the connected PCFs.
关键词： optical fibers control,optical power loss,photonic crystal fiber,optical fiber connection,autoconvolution method,mode field,near-field technique
更新于2025-09-23 15:19:57
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Evaluation of performance of near-field thermophotovoltaic systems based on entropy analysis
摘要： Near-field radiative heat transfer can significantly improve the output power of thermophotovoltaic (TPV) systems. Therefore, it is crucial to explore how to increase the energy conversion efficiencies of near-field TPV systems. In this study, based on the fluctuation–dissipation theorem with the effective medium theory, we evaluate the performance of a near-field TPV system from the formulation of thermodynamics. It is found that a near-field TPV system consisting of InAs or GaSb cell can achieve higher heat flux or efficiency limit, respectively. Moreover, the TPV system with a hyperbolic metamaterial (HMM) emitter composed of nanowire or nanohole arrays can achieve higher heat flux and efficiency limit compared to that of the bulk reference. This is attributable to the HMMs being able to support hyperbolic modes, and the radiation with the HMM emitter exhibits a favorable entropy content for the energy conversion efficiency. This work provides an approach to determine the efficiency limit and establish a target for efficiency of the near-field TPV system without considering how the system works. The results of this study will facilitate the design and application of the HMM emitter and material of the TPV cell to improve the efficiency of near-field TPV systems.
关键词： Thermophotovoltaic systems,Near-field radiative heat transfer,Energy conversion efficiency,Hyperbolic metamaterial,Entropy analysis
更新于2025-09-23 15:19:57
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Molecular States of Composite Fermions in Self-Organized InP/GaInP Quantum Dots in Zero Magnetic Field
摘要： The size and positions of regions of line localization and the magnetic-field (0–10 T) dependence of the low-temperature (10 K) photoluminescence spectra of single InP/GaInP quantum dots with a number of electrons of N = 5–7 and a Wigner–Seitz radius of ~2.5 are determined using a near-field scanning optical microscope. The formation of composite fermion molecules with a size coinciding with that of localization regions and bond lengths of ~30 and 50 nm, respectively, at a Landau-level filling factor from 1/2 to 2/7 in zero magnetic field is established. At N = 6, the pairing and rearrangement of composite fermions under photoexcitation are found, which offers opportunities for the use of InP/GaInP quantum dots to create a magnetic-field-free topological quantum gate.
关键词： InP/GaInP quantum dots,near-field scanning microscopy,photoluminescence,composite fermions,topological quantum gate
更新于2025-09-23 15:19:57
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A Preamplifier for a CdHgTe Photodetector
摘要： A preamplifier for operation with an HgCdTe-based nitrogen-cooled IR photodetector (600 nm–15 μ m) is described. The preamplifier operates in the photoconductivity mode. The use of modern microcircuits made it possible to increase the bandwidth of the response to 2 MHz at a noise level of 0.5 nV/Hz1/2, which is close to the fundamental limit that is specified by the resistance of the photosensitive element. The preamplifier was used in an aperture-free scanning near-field optical microscope.
关键词： HgCdTe,IR photodetector,scanning near-field optical microscope,photoconductivity,preamplifier
更新于2025-09-23 15:19:57
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Plasmonic Nanostructures for Photothermal Heating and Near-Field Enhancements: A Comparative Survey of Nineteen Metals
摘要： Localized surface plasmon resonances (LSPRs) optically excited in metallic nanoparticles (NPs) produce beneficial thermal and non-thermal effects. Non-thermal effects, such as enhancing and localizing fields on subwavelength scales and photo-generating hot carriers, have been extensively exploited, while interest in highly localized photothermal heating is reviving. Both effects may work together synergistically, such as increasing the efficiency of a photocatalytic process, or they may work against each other, such as accelerating desorption of analytes in surface enhanced spectroscopy. To compare how these effects depend on the composition and size of the NP, we report a quantitative survey of thermal and non-thermal properties in the visible-solar (1.7–4.1 eV) and UV (3.1-6.2 eV) ranges for nineteen metals, including conventional plasmonic materials (gold, silver, copper), an alkaline earth metal (magnesium), post-transition metals (aluminum, gallium, indium), and a wide variety of transition metals. Figures of merit that reflect the resistive losses and electric field enhancement factor of the NPs were used in this comparative analysis.
关键词： Photothermal heating,Nanoparticles,Near-field enhancements,Plasmonics,Metals
更新于2025-09-23 15:19:57
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Near-Field Radiative Heat Transfer between Dissimilar Materials Mediated by Coupled Surface Phonon- and Plasmon-Polaritons
摘要： Near-field radiative heat transfer (NFRHT) between dissimilar materials supporting surface polaritons in the infrared is of critical importance for applications such as photonic thermal rectification and near-field thermophotovoltaics. Here, we measure NFRHT between millimeter-size surfaces made of 6H-SiC and doped Si, respectively supporting surface phonon-polaritons (SPhPs) and surface plasmon-polaritons (SPPs) in the infrared, separated by a 150-nm-thick vacuum gap spacing maintained via SiO2 nanopillars. For purpose of comparison, measurements are also performed between two doped Si surfaces. The measured radiative flux is in good agreement with theoretical predictions based on fluctuational electrodynamics. A flux enhancement beyond the blackbody limit of ~ 8.2 is obtained for the SiC-Si sample, which is smaller than the enhancement for the Si-Si sample (~ 12.5) owing to the spectral mismatch of the SiC and Si light lines, and SPhP and SPP resonances. However, due to lower losses in SiC than Si and weaker SPhP-SPP coupling than SPP coupling, the near-field enhancement for the SiC-Si sample exhibits a more pronounced monochromatic behavior with a resonant flux that is ~ 5 times larger than the resonant flux for the Si-Si sample. This work demonstrates that it is possible to modulate NFRHT via surface polariton coupling, and will accelerate the development of energy conversion and thermal management devices capitalizing on the near-field effects of thermal radiation between dissimilar materials.
关键词： radiative flux measurement,doped silicon,near-field radiative heat transfer,dissimilar materials,coupled surface phonon- and plasmon-polaritons,silicon carbide
更新于2025-09-23 15:19:57
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Correlation between Near-Field Enhancement and Dephasing Time in Plasmonic Dimers
摘要： Near-field enhancement and dephasing time play critical roles in several applications of localized surface plasmon resonance. Here, using an example gold dimer system, we reveal the correlation between the near-field enhancement and dephasing time via time-resolved photoemission electron microscopy. Compared with isolated particles, dimers with small gap sizes show stronger near-field enhancement and shorter dephasing times. These results are well reproduced by numerical simulations and further explained by a coupled dipole approximation model. The roles of near- and far-field coupling and plasmon localization in balancing near-field enhancement and dephasing time are also unveiled.
关键词： dephasing time,time-resolved photoemission electron microscopy,near-field enhancement,plasmonic dimers,coupled dipole approximation model
更新于2025-09-23 15:19:57
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Subcellular chemical imaging of structurally similar acridine drugs by near-field laser desorption/laser postionization mass spectrometry
摘要： Insights into the pharmacologic effect on cellular processes and the potential toxicological effects are vital to new drug development and evaluation, yet research on these subjects remains a great challenge due to the lack of information regarding the spatiotemporal distribution of drugs and metabolites within a single cell. Mass spectrometry imaging (MSI) has proven to be a label-free and high-throughput approach for visualizing drug distribution in spatial and temporal domains. However, single-cell drug imaging has been limited so far by detection sensitivity and microscale lateral resolution. Herein, we report near-field laser desorption/laser postionization mass spectrometry (NDPI-MS) for single-cell imaging of two structurally similar drugs, proflavine and ethacridine, and subcellular distributions of proflavine at different drug concentrations were investigated. The NDPI-MS imaging results indicate that proflavine was accumulated in lysosomes, which was verified by laser scanning confocal microscopy (LSCM). Additionally, a distinguished subcellular distribution pattern of ethacridine from proflavine could be visualized, highlighting the complexity of the interaction between the drugs and biological environment even though these two drugs possess similar structures. Taken together, the present results demonstrate the great potential of the integrated single-cell MSI platform for characterizing the drug distribution and its phenotype changes within individual cells, expediting the identification and evaluation of newly developed drugs.
关键词： single cell imaging,mass spectrometry,acridine drugs,laser postionization,near-field
更新于2025-09-23 15:19:57
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Nanoscale Characterization of Surface Plasmon-Coupled Photoluminescence Enhancement in Pseudo Micro Blue LEDs Using Near-Field Scanning Optical Microscopy
摘要： The microcave array with extreme large aspect ratio was fabricated on the p-GaN capping layer followed by Ag nanoparticles preparation. The coupling distance between the dual-wavelength InGaN/GaN multiple quantum wells and the localized surface plasmon resonance was carefully characterized in nanometer scale by scanning near-field optical microscopy. The effects of coupling distance and excitation power on the enhancement of photoluminescence were investigated. The penetration depth was measured in the range of 39–55 nm depending on the excitation density. At low excitation power density, the maximum enhancement of 103 was achieved at the optimum coupling distance of 25 nm. Time-resolved photoluminescence shows that the recombination life time was shortened from 5.86 to 1.47 ns by the introduction of Ag nanoparticle plasmon resonance.
关键词： near-field scanning optical microscopy,micro-LEDs,localization surface plasmon
更新于2025-09-23 15:19:57
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Near-Field Imaging Analysis of Three-Dimensional MIMO Array
摘要： This paper presents a MIMO imaging system, which has good imaging effect and higher resolution. The equations for the position of antennas are deduced in detail. The proposed algorithm is used to carry out inverse scattering microwave image through the near-field scattered electric field which is obtained by the simulation software. The formulas of imaging resolution of MIMO antenna array are presented in this paper. The main factors which influence the quality of the image are analyzed, and the accuracy and feasibility of the resolution formula are verified by the simulation of complex object, which provides a valuable reference method for the actual microwave imaging system.
关键词： MIMO imaging system,microwave imaging,resolution,near-field imaging,antenna array
更新于2025-09-23 15:19:57