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The Sensing Applications in U-Shape Structure Based on Dual Transparency Windows
摘要： We have researched a U-shape structure that consists of three vertical cavities coupled with bus wave-guide. The theoretical results based on the coupled mode theory are consistent with simulation results. We demonstrate that the interaction among two bright and one dark modes lead to dual plasmon induced transparency. Meanwhile, it is found that the lateral displacement S plays an important role in the transmission property, and the transmission dip with different transmittance in various lateral displacement S has been explained theoretically. Moreover, the nano sensor has a sensitivity of 1225 nm shift per refractive index unit, and the ?gure of merit is up to 62.5. The proposed structure has the advantages of simple and compact structure, easy fabrication, and the ultra-compact structure holds great potential to the control of light in highly integrated optical circuits and nano sensor.
关键词： Surface plasmons,nano sensors,coupled mode theory
更新于2025-09-23 15:23:52
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Asymptotic approximations for the plasmon resonances of nearly touching spheres
摘要： Excitation of surface-plasmon resonances of closely spaced nanometallic structures is a key technique used in nanoplasmonics to control light on subwavelength scales and generate highly confined electric-field hotspots. In this paper, we develop asymptotic approximations in the near-contact limit for the entire set of surface-plasmon modes associated with the prototypical sphere dimer geometry. Starting from the quasi-static plasmonic eigenvalue problem, we employ the method of matched asymptotic expansions between a gap region, where the boundaries are approximately paraboloidal, pole regions within the spheres and close to the gap, and a particle-scale region where the spheres appear to touch at leading order. For those modes that are strongly localised to the gap, relating the gap and pole regions gives a set of effective eigenvalue problems formulated over a half space representing one of the poles. We solve these problems using integral transforms, finding asymptotic approximations, singular in the dimensionless gap width, for the eigenvalues and eigenfunctions. In the special case of modes that are both axisymmetric and odd about the plane bisecting the gap, where matching with the outer region introduces a logarithmic dependence upon the dimensionless gap width, our analysis follows Schnitzer [Singular perturbations approach to localized surface-plasmon resonance: nearly touching metal nanospheres. Phys. Rev. B 92(23), 235428 (2015)]. We also analyse the so-called anomalous family of even modes, characterised by field distributions excluded from the gap. We demonstrate excellent agreement between our asymptotic formulae and exact calculations.
关键词： asymptotic analysis,eigenvalue problems,Surface plasmons
更新于2025-09-23 15:22:29
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Performance study of surface plasmon resonance and lossy mode resonance based fiber optic sensors utilizing silver and indium oxide layers: An experimental investigation
摘要： This study presents here the experimental investigations on a surface plasmon resonance (SPR)/lossy mode resonance (LMR) based fiber optic sensors coated with silver and indium oxide layers. Different sensing probes have been fabricated by coating (i) a single layer of indium oxide, (ii) a single layer of silver and (iii) a double layer of indium oxide and silver (with different thicknesses) symmetrically onto to the bare core of silica fiber. The sensitivity of these fiber optic sensing probes towards surrounding region refractive index variations are determined using different concentrations of sucrose solutions. It was found that sensor probe fabricated with coating of 100 nm thickness of indium oxide was two times more sensitive than the conventionally used fiber optic sensing probe coated with only silver layer. The sensitivity of a double layer coated fiber optic sensor with various thicknesses of indium oxide and silver layers is in between the two extremes of the sensitivities. This study will find suitable applications in the field of chemical and biochemical sensing. The drawbacks of silver coatings and the advantages of LMR supporting indium oxide have also been discussed.
关键词： Surface plasmons,Sensitivity,Lossy mode resonances,Thin films,Fiber optic sensors,Detection accuracy,Indium oxide
更新于2025-09-23 15:21:21
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Broadband light harvesting for highly efficient hot-electron application based on conformal metallic nanorod arrays
摘要： The utilization of nonradiative decay of surface plasmons (SPs) in the form of hot electrons in metallic nanostructures has a great potential for applications in photovoltaics, photocatalysis, photodetection, and surface imaging. Unfortunately, the metallic nanostructures usually support only narrowband plasmon resonances; moreover, the hot-electron thermalization loss during the transport to Schottky interface and the confined momentum space for hot-electron injection into semiconductor together result in an inefficient internal quantum process. In this study, we propose and experimentally demonstrate a broadband super absorber based on the metallic nanorod arrays (NRs). Optically, the average absorption across the entire visible band is up to 0.8, which is over 16-fold enhancement of the planar reference. Electrically, the hot electrons are controlled to be preferentially generated near Schottky interface within the mean free path, relieving the severe hot-electron thermalization loss. Moreover, the three-dimensional Schottky junction provides much increased hot-electron momentum space for injection at the vertical surface. These optical and electrical benefits lead to over 30-fold enhancement in the IPCE (incident photon-to-electron conversion efficiency) relative to the reference. The IPCE can be up to 10.9% at Eph = 3.1 eV, which is close to the limit of the thick-film single-barrier hot-electron devices. The conformal NRs system provides a promising strategy to simultaneously improve the hot-electron generation, transport and collection efficiencies and could be an outstanding candidate for efficient hot-electron optoelectronic and photocatalysis systems.
关键词： hot electron,surface plasmons,nanorod arrays,broadband absorber
更新于2025-09-23 15:21:21
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Correlative Study of Enhanced Excitonic Emission in ZnO Coated with Al Nanoparticles using Electron and Laser Excitation
摘要： Recently, metal nanoparticle surface coatings have been found to significantly enhance the ultra-violet luminescence intensity from ZnO, providing a viable means to mitigate optical losses and improve LED performance. Although there is general agreement that resonantly excited Localized Surface plasmons (LSps) in metal nanoparticles can directly couple to excitons in the semiconductor increasing their spontaneous emission rate, the exact mechanisms involved in this phenomenon are currently not fully understood. In this work, LSP-exciton coupling in bulk and nanostructured ZnO coated with a 2 nm Al nanoparticle layer is investigated using correlative photoluminescence and depth-resolved cathodoluminescence and time-resolved photoluminescence spectroscopy. Temperature-resolved cathodoluminescence and photoluminescence measurements from 10 K to 250 K show free exciton (FX) emission enhancement factors up to 12x at 80 K, and reveal that the FX couple more efficiently to the LSPs compared to the localized donor-bound excitons. A strong polarization dependence between the LSPs and FX is observed where FX transitions are more strongly enhanced when polarized in the same direction as the electric field of the incident excitation, which is different for laser and electron beam sources. This result indicates that selective enhancement of the excitonic emission peaks in the ZnO coated with Al nanoparticles can be achieved by choosing the appropriate ZnO substrate orientation.
关键词： Localized Surface plasmons,metal nanoparticle,ZnO,exciton coupling,luminescence
更新于2025-09-23 15:21:01
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Quantum dot based mid-infrared photodetector enhanced by a hybrid metal-dielectric optical antenna
摘要： Surface plasmon waves and Rayleigh anomaly are characteristic optical phenomena exhibited by periodic subwavelength grating structures. In this paper, a hybrid metal-dielectric metasurface is proposed to improve the photoresponse of Ge/Si quantum dot infrared photodetectors (QDIPs) with the limited absorption layer thickness. The composite metasurface consists of a regular array of silicon pillars. The pillars protrude through subwavelength holes in a perforated gold ?lm on detector top. We demonstrate that by combining e?ects of dielectric and plasmonic metal components, the QDIP photoresponse can be signi?cantly improved compared to case when all-dielectric and metal gratings work alone. We observe about 4 times photoresponse enhancement with the hybrid metasurface device relative to a common plasmonic design with the two-dimensional metal hole array. Compared with a bare QDIP, the peak responsivity of the hybrid detector at a wavelength of 4.4 μm is increased by a factor of 15. The enhanced sensitivity is supposed to arise from coupling of the surface plasmon resonance and di?ractive e?ect related to the Rayleigh anomaly.
关键词： infrared photodetection,quantum dots,surface plasmons,enhancement,near-?eld
更新于2025-09-23 15:21:01
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Plasmonics || Plasmonic Modes in Au and AuAg Nanowires and Nanowire Dimers Studied by Electron Energy Loss Spectroscopy
摘要： In this chapter, we review our recent work on the investigation of surface plasmon modes in metallic nanowires and nanowire dimers by means of electron energy loss spectroscopy combined with scanning transmission electron microscopy (STEM-EELS). Due to the very high spatial resolution, STEM-EELS is a powerful technique to visualize multipole order surface plasmon modes in nanowires and study the dependency of their resonance energies on different parameters such as nanowire dimensions or nanowire porosity. In addition, we investigate surface plasmon hybridization in nanowires separated by gaps of less than 10 nm or connected by small metallic bridges. In such structures new modes arise, which depend strongly on gap or bridge sizes. Experimental results are supported by finite element simulations. The investigated nanowires and dimers are fabricated by electrodeposition in etched ion-track templates, combined with a selective dissolution processes. The synthesis techniques and their advantages for the fabrication of plasmonic nanostructures are also discussed.
关键词： nanowire dimers,scanning transmission electron microscopy,ion-track technology,electron energy loss spectroscopy,nanogaps,nanowires,electrodeposition,plasmon hybridization,etched ion-track membranes,surface plasmons,gold
更新于2025-09-23 15:21:01
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Optimizing the performance of ZnO/Au/MgZnO/SiO2 sandwich structured UV photodetectors by surface plasmons in Ag nanoparticles
摘要： The dual-wavelength UV photodetector (PD) with sandwich structure of ZnO/Au/MgZnO/SiO2 was fabricated and investigated with an emphasis on the effects of the Ag nanoparticles localized surface plasmons (LSPs). The results demonstrated that the modification in Ag nanoparticle (NP) position played a remarkable influence on the performance of dual-wavelength UV photodetectors. In comparison with decorating Ag NPs on the surface of the PDs, embedding Ag NPs between the MgZnO and ZnO films could improve two peak responsivities (caused by MgZnO and ZnO layers) significantly. By calculating the responsivities enhancement ratio of double layers (MgZnO and ZnO), the results indicated that the enhancement ratio of MgZnO is higher than that of ZnO. This was ascribed to LSPs of energy match with MgZnO which was superior to ZnO. This work described a creative method for increasing the performance of dual-wavelength UV PDs.
关键词： MgZnO,Ag nanoparticles,Dual wavelength,ZnO,Surface plasmons,UV photodetectors
更新于2025-09-23 15:21:01
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Phenomena of Optical Metamaterials || Disorder in Metamaterials
摘要： Since the emergence of the metamaterial, the disorder within artificially structured materials has been a subject of extensive discussions. Metamaterial at optical frequency can be considered as a kind of man-made architecture material possessing unusual properties. One of its remarkable features is that the equivalent permittivities on different directions differ from each other and can be varied by designing its structure elaborately. It is worthwhile mentioning that this property is enhanced by the presence of the disorder promises that metamaterial may serve for surface plasmons (SPs) propagating with more flexible performances than conventional metal or ordered metamaterial. For instance, dealing with the photonic crystals, some disorder can dramatically degrade the reflection and transmission properties, which are based on constructive interferences. This chapter covers three different models of the disordered metamaterials: (i) rotational disorder, (ii) sliding disorder, and (iii) positional disorder.
关键词： sliding disorder,rotational disorder,positional disorder,surface plasmons,metamaterials,disorder
更新于2025-09-23 15:21:01
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Stretchable and Higha??Adhesive Plasmonic Metasheet Using Al Subwavelength Grating Embedded in an Elastomer Nanosheet
摘要： Plasmonic metasurfaces have attracted much attention for use in device applications over the past decade. Dynamic color tuning (DCT), where the displacement of periodic nanostructures is controlled to generate different colors in real time, is one of the great possibilities of plasmonic metasurfaces for optical strain sensors or display devices. In this study, an Al metasurface embedded in an elastomer nanosheet with film thickness 400 nm is fabricated by means of sacrificial release using a polyvinyl alcohol sacrificial layer. This plasmonic metasheet shows not only the seven colors produced by surface plasmons, but also DCT by stretching the elastomer nanosheet. Each pixel, designed with a grating period of 300–600 nm, emits the bright colors expected in electromagnetic simulation. Moreover, stretching the plasmonic metasheet demonstrates DCT from 495 to 660 nm in the visible light range. The freestanding metasheet with maximum thickness 400 nm may be easily integrated into any active device by post-processing transfer. Stretching the metasheet requires an estimated × 10?3 lower force than previously reported for plasmonic metasurfaces, owing to a film thickness of only several hundreds of nanometers. These results facilitate the realization of microdevices with novel capabilities based on plasmonic metamaterials.
关键词： plasmonic metamaterials,elastomer nanosheets,dynamic color tuning,subwavelength gratings,surface plasmons
更新于2025-09-23 15:21:01