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Control of plasmon dephasing time using stacked nanogap gold structures for strong near-field enhancement
摘要： The construction of metallic nanostructures with strong near-field enhancement is becoming increasingly significant for the practical use of plasmonic devices, such as plasmonic sensors and light-energy conversion systems. Importantly, the near-field enhancement effect depends on the plasmon dephasing time. Here, we propose a method for controlling plasmon dephasing time by utilizing plasmonic coupling for stronger near-field enhancement. Ordered arrays of stacked nanogap gold (Au) structures composed of a metal/insulator/metal nanostructure were fabricated by electron beam lithography and dry etching processes on a niobium-doped titanium dioxide substrate. The dark plasmon mode was excited by the near-field coupling between the upper and lower Au nanostructures separated by an alumina layer with a thickness of 15 nm. A strong near-field enhancement effect was induced by the localization of the electromagnetic field between the upper and lower Au nanostructures and the longer plasmon dephasing time based on the excitation of the dark plasmon mode. It is noteworthy that the dephasing time of the dark plasmon mode measured by time-resolved photoemission electron microscopy was extended 3-fold compared with that of the plasmon mode of the Au nanoblock, which can be controlled by the structural design of the stacked nanogap Au structures.
关键词： Dark plasmon mode,Plasmon dephasing,Near-field enhancement,Photoemission electron microscopy (PEEM),Surface plasmon resonance
更新于2025-09-23 15:23:52
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Discrepancies and universality in the fractional reduction of the apex-field enhancement factor considering small clusters of field emitters
摘要： Numerical simulations are important when assessing the many characteristics of field emission related phenomena. In this work, we analyze the fractional change of the apex-Field Enhancement Factor (FEF), ??, from a single emitter, with apex-FEF ??1, and a pair, with apex-FEF ??2. We show, based on finite element technique, that the functional dependence ??(??) (?? corresponding to the distance between the axis of the emitters) obeys a recently proposed power law decay [1], at sufficient large distances in the limit of infinite domain size, which is not observed by using a long time established exponential decay [2] or a more sophisticated fitting formula proposed recently by Harris et al. [3]. This inverse-third power law functional dependence is respected for various systems like infinity arrays and small clusters of emitters with different shapes. Thus, ??? ～ ?????, with ?? = 3, is suggested to be a universal signature of the charge-blunting (CB) effect in small clusters or arrays, at sufficient large distances between emitters with any shape. These results improve the physical understanding of the field electron emission theory to accurately characterize emitters in small clusters or arrays.
关键词： charge-blunting effect,power law decay,apex-Field Enhancement Factor,field emission,numerical simulations
更新于2025-09-23 15:21:21
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Nanoparticle using parallel split rings and implementation of chain for creating Fano resonance with polarization independence for energy harvesting in mid-infrared
摘要： In optical devices, the polarization of the incident wave affects the Nano particle characteristics. Therefore, designing a polarization-independent device is significant in the process of designing optical structures. On the other hand, the concept of Fano resonance and dark mode has been utilized for achieving more energy enhancement. In this paper, we have developed a symmetrical Nano antenna by employing Fano resonance, which is independent of the incident wave polarization. The proposed Nano antenna is modified in mid infrared regime for biosensing and energy harvesting applications. The designed metamaterial antenna is made by Nano split ring resonators with etched capacitive gaps, which are utilized for concentrating energy. The introduced Nano antenna has a bright and dark mode with a weak enhancement of electric field. The effect of the incident wave polarization is investigated at wave incident angles between 0° and 45° to illustrate the independency of the polarization due to the symmetrical shape of the Nano antenna. In order to trigger the dark mode and enhance the electric field, a Nano chain is incorporated in the final structure. This arrangement has led to increasing of electric field drastically. Furthermore, the figure of merit has been calculated as an advantageous factor in sensing the surrounding materials with various refractive indices. Our findings illustrated that the chain arrangement has caused a peak in the linear form of the extinction cross section of the Nano antenna. This in turn has resulted in the appearance of Fano resonance with no impact on the resonance frequency that has been originally adjusted by capacitive gaps and inductive strips.
关键词： FANO resonance,Dark mode,Controllable field enhancement,Plasmonic
更新于2025-09-23 15:21:21
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Gap Plasmon of Virus-Templated Biohybrid Nanostructures Uplifting the Performance of Organic Optoelectronic Devices
摘要： Plasmonic nanostructures, which exhibit prominent localized surface plasmon resonance (LSPR) properties, are highly desirable for organic solar cells (OSC) and organic light-emitting diode (OLED) devices. In the present work, novel plasmonic bio-nanostructures are successfully synthesized via the self-densification of silver (Ag) and gold (Au) metallic nanoparticles (NPs) onto a genetically engineered M13 bacteriophage template. Owing to the unique charge selectivity of the peptide receptors on the M13 bacteriophage, the metallic NPs can be directly anchored onto the bacteriophage through charge-driven interactions without binder/surfactant. The resulting Ag/AuNP-M13 bio-nanostructures display extraordinary gap-plasmon effect as well as tremendously enhanced LSPR properties than the randomly dispersed Ag/Au NPs. The incorporation of Ag/AuNP-M13 bio-nanostructures tremendously improves the performance of both OSC and OLED devices. Specifically, a power conversion efficiency increment of 15.5% is recorded for the phage-modified OSCs; whereas an external quantum efficiency increment of 22.6% is achieved for the phage-modified OLEDs. Based on this environmentally benign virus-template approach, various plasmonic/photonic bio-nanostructures can be designed for diverse device applications.
关键词： field-enhancement,optoelectronics,M13 bacteriophage,metamaterials,self-assembly,gap-plasmon effect
更新于2025-09-23 15:21:01
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Topology Optimization-Based Inverse Design of Plasmonic Nanodimer with Maximum Near-Field Enhancement
摘要： The near-field enhancement factor is one of the most significant parameters to evaluate the performance of plasmonic nanostructures. Numerous efforts have been made to maximize the enhancement factor through optimizing the size, shape, and spatial arrangement of metallic nanostructures with simple geometries, such as disk, triangle, and rod. This work implements topology optimization to inversely design a metallic nanoparticle dimer with the goal of optimizing the near-field enhancement factor in its sub-10 nm gap. By optimizing the material layout within a given design space, the topology optimization algorithm results in a plasmonic nanodimer of two heart-shaped particles having both convex and concave features. Full-wave electromagnetic analysis reveals that the largest near-field enhancement in the heart-shaped nanoparticle dimer is originated from the greatest concentration of surface charges at the nano-heart apex. Inversely designed heart-, bowtie-, and disk-shaped nanodimers are fabricated by using focused helium ion beam milling with a “sketch and peel” strategy, and their near-field enhancement performances are characterized with nonlinear optical spectroscopies at the single-particle level. Indeed, the heart-shaped nanodimer exhibits much stronger signal intensities than the other two structures. The present work corroborates the validity and effectiveness of topology optimization-based inverse design in achieving desired plasmonic functionalities.
关键词： topology optimization,near-field enhancement,plasmonic nanostructures,inverse design,nonlinear optics
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Electric Field Enhancement from Semiconductive Protrusions in Extruded Power Cables
摘要： The paper deals with calculation of the field enhancement from semiconductive protrusions in high voltage polymeric cables. The scientific community has traditionally used two different equations: The Larmor formula assuming spheroidal shape of the protrusion and the Mason formula assuming hyperboloidal shape. The Larmor equation can only be used for sharp protrusions (small tip radius) that are not representative for the majority of the protrusions found in power cables. On the other hand, the Mason equation has not this restriction, but can give values very much different from those obtained by the Larmor formula. It will be emphasized in the paper that the Mason formula was derived for needle-plane geometries and is therefore not valid for estimation of the field enhancement of protrusions extending into the insulation from a conductive plane. On the other hand, the Larmor formula follows from the analytical solution of the Laplace equation for the electric field outside a spheroidal-shaped protrusion in a plane-plane geometry. It is thus the best available formula for calculating field enhancement from semiconductive protrusions in high voltage cables. The paper will also introduce a new solution to the Laplace equation making it possible to extend the Larmor equation to spheroidal protrusions of all shapes, including those typical for modern cables.
关键词： Power cables,field enhancement,protrusions
更新于2025-09-23 15:21:01
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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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Enhanced field electron emission of single-walled carbon nanotubes prepared by imprinting technique
摘要： In this work, single-walled carbon nanotubes (SWCNTs) field electron emitters were fabricated by imprinting SWCNTs on substrates with a silver buffer layer. It was found that the field emission properties of imprinted SWCNTs were significantly improved with turn-on field at 0.62 V/um and threshold field at 1.04 V/um, comparing to screen-printed SWCNTs emitters who had turn-on field at 1 V/um and threshold field at 2 V/um. These improvements of SWCNTs emitters were owing to the directly imprinting method which made SWCNTs have clean surface and more emitters on the substrates. The lower turn-on electric field of field emission was attributed to no impurities encapsulate on the emitters and the large aspect ratio of SWCNTs resulting in high field enhancement factor of 15800. The emission performance of the imprinted cathode was almost unchanged after many times repeated experiments. This simple and low cost technique can fabricate high performance field emission cathodes efficiently and also demonstrates potential applications in many electronic devices.
关键词： Field enhancement factor,Turn-on field,Imprinting,Field emission,Single-walled carbon nanotubes,Temporal stability
更新于2025-09-19 17:13:59
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Plasmonic Nanoparticle Film for Low-Power NIR-Enhanced Photocatalytic Reaction
摘要： Plasmonic metal nanostructures offer the unique ability to effectively enhance sunlight harvesting by localized surface plasmon resonance (LSPR), which can induce direct photocatalytic reactions. However, only metal nanoparticles with a relatively low magnitude of electromagnetic field enhancement usually require a high illumination intensity to ensure the catalytic performance, which greatly limits the solar photocatalytic efficiency. Herein, we designed plasmonic Au nanoparticle film with high electromagnetic field enhancement to achieve high-efficiency catalytic activity under low power NIR light illumination. This work minimized the influence of the photothermal effect on the reaction by using a low illumination intensity and further revealed the main contribution of plasmon-excited hot electrons to the photochemical reaction. This study provides important insights into the study of the mechanism of LSPR in photocatalytic reactions and further improves the efficiency of solar energy utilization.
关键词： Localized surface plasmon resonance,hot electrons,low power illumination,electromagnetic field enhancement,NIR photocatalysis
更新于2025-09-19 17:13:59
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Nucleic acid hybridization on a plasmonic nanointerface of optical microfiber enables ultrahigh-sensitive detection and potential photothermal therapy
摘要： Quantifying the microRNA (miRNA) level and manipulating them in complex samples, such as serum, is of intense interest because miRNAs are important diagnostic markers. Here, we demonstrate an optical microfiber integrating of untrasensitive detection function and local photothermal therapy potential. A nanointerface consisting of GO supported Cu2-xS nanoplates presented the localized surface plasmon resonance (LSPR) tuned to be consistent with the operation wavelength of the microfiber transducer. It enhanced the surface energy density of evanescent field, on which the miRNA sensing and therapy occurred. With evanescent field enhancement by the plasmonic nanointerface, the sensor exhibits an ultrahigh sensitivity for detecting microRNA at concentrations ranging from 0.1 aM to 10 pM. It is also capable of differentiating one-base mismatches of miRNA at ultralow concentrations (as low as 10 aM) in serum. The photothermal effect of nanointerface simultaneously endows the sensor with the potential for localized photothermal therapy. This work presents a possible approach for the in-situ integration of diagnosis and treatment in early stage.
关键词： optical microfiber sensor,integrating functions,graphene-oxide supported Cu2-xS nanointerface,potential photothermal therapy,evanescent field enhancement
更新于2025-09-19 17:13:59