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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) - Towards Near-Field Coupling of Surface Plasmon Polaritons across Few-Nanometer Gaps between two Laterally Tapered Gold Waveguides
摘要： Nanofocusing of light in combination with an efficient energy transfer of metallic nanostructures is a key task towards ultrafast, all-optical switching on the nanoscale. A possible realization of such a device is based on two tapered plasmonic nanostructures separated by a few-nanometer gap, in which information transport is controlled via strong coupling of the electromagnetic near-field and excitonic molecules in the gap region of the waveguides. The fabrication of such mesoscopic nanostructures that can concentrate free-propagating light to few-nanometers dimensions remains challenging due to the desired nanometer precision in the gap region. Here, we report on the fabrication of a plasmonic nanostructures consisting of a pair of both striped and tapered waveguides in 200 nm thick Au films with gap sizes and radii of curvature down to 11 nm using a Focused Ion Beam-based “Sketch and Peel” lithography process. Curved focused-ion beam written gratings in the waveguides enable the in- and out-coupling and focusing of surface plasmon polaritons into the nanostructure. The propagation of these SPPs is afterwards monitored using far-field confocal microscopy. We find a relatively constant transmission of light for large gap sizes, accompanied by a drastically increase for gap sizes below 20 nm. This increase for small gap sizes can be approximated best by fitting an exponential decay with a decay length of 8 nm suggesting a significant energy transport through near-field coupling of the two waveguides. These experimental findings are in accordance to finite element method and finite difference time domain calculations that show a strong localization of the electric field in the gap region of the two waveguides. The profound electric field strength and the spatial confinement of the electric fields suggest such plasmonic waveguides as prototypical structures for probing the strong coupling between propagating surface plasmon polaritons in adjacent, however separated plasmonic waveguides on one hand and between SPP waves and single quantum emitters that are placed in the gap region of the waveguides on the other hand. The realization of such coupling could enable the ultrafast, remote switching on the nanoscale.
关键词： ultrafast switching,nanofocusing,near-field coupling,surface plasmon polaritons,plasmonic nanostructures
更新于2025-09-16 10:30:52
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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) - Fabrication of High Quality Quantum Emitters in Diamond Nanostructures
摘要： As the field of solid-state quantum engineering matures, it is increasingly necessary to produce quantum emitters with narrow optical transitions and long spin coherence times aligned to nanophotonic structures. The nitrogen-vacancy (NV) defect center in diamond is a well-suited candidate owing to a spin ground state with a long coherence time, nearby nuclear spins for quantum memories, and spin-selective optical transitions allowing for efficient optical spin initialization and readout. We demonstrate an emitter-device alignment technique enabling fabrication of photonic devices registered to NVs. The alignment method relies on autonomously imaging emitters and registering them relative to an on-chip coordinate system. This technique can be performed on a large variety of emitters. The repeatability of this method suggests a spatial accuracy of 50 nm. The ability to navigate a sample autonomously facilitates data collection on a large number of NVs, thus permitting statistical analyses. We utilized this approach to correlate the NV’s host nitrogen isotope with the optical linewidth of the emitter to understand the effects of implantation. As shown in Fig. 1a, the data indicate that the coherent, narrow-linewidth NVs are formed from naturally abundant nitrogen (14N), whereas the implanted nitrogens (15N), on average, yield broader linewidth NVs. The implanted 15NVs also exhibit larger axial and transverse strains suggesting that damage was produced near the emitter. We attribute the broad linewidths of implanted 15NVs to a more volatile local environment generated by local damage resulting from the ion implantation process.
关键词： diamond nanostructures,nanophotonic structures,nitrogen-vacancy center,spin coherence,quantum emitters
更新于2025-09-16 10:30:52
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Nonlinear absorption and scattering of a single plasmonic nanostructure characterized by <i>x</i> -scan technique
摘要： Nonlinear nanoplasmonics is a largely unexplored research area that paves the way for many exciting applications, such as nanolasers, nanoantennas, and nanomodulators. In the field of nonlinear nanoplasmonics, it is highly desirable to characterize the nonlinearity of the optical absorption and scattering of single nanostructures. Currently, the common method to quantify optical nonlinearity is the z-scan technique, which yields real and imaginary parts of the permittivity by moving a thin sample with a laser beam. However, z-scan typically works with thin films, and thus acquires nonlinear responses from ensembles of nanostructures, not from single ones. In this work, we present an x-scan technique that is based on a confocal laser scanning microscope equipped with forward and backward detectors. The two-channel detection offers the simultaneous quantification for the nonlinear behavior of scattering, absorption and total attenuation by a single nanostructure. At low excitation intensities, both scattering and absorption responses are linear, thus confirming the linearity of the detection system. At high excitation intensities, we found that the nonlinear response can be derived directly from the point spread function of the x-scan images. Exceptionally large nonlinearities of both scattering and absorption are unraveled simultaneously for the first time. The present study not only provides a novel method for characterizing nonlinearity of a single nanostructure, but also reports surprisingly large plasmonic nonlinearities.
关键词： nonlinear absorption,absorption cross section,nonlinear scattering,single gold nanostructures,laser scanning microscopy,nanoplasmonics
更新于2025-09-16 10:30:52
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Synergic effect of plasmonic gold nanoparticles and graphene oxide on the performance of glucose sensing
摘要： In this study hybrid nanostructures of Au–graphene oxide (Au–GO) were synthesized via a two-step process and used to modify the glassy carbon electrode (GCE) for electrochemical measurements of glucose. The modified electrode exhibits a fast response less than 4 s, a low detection limit of 0.025 mM and a high signal-to-noise ratio (S/N) of 3.5. The fabricated sensor shows a linear response in a large concentration range from 0.0025 mM to 15 mM with a reproducible sensitivity of 84.53 mA cm?2 mM?1, which is much higher than that of the individual Au, GO and previously reported GO/rGO based sensors. In addition, the biosensor shows excellent results for human serum which agree well with those obtained using a laboratory glucometer. Moreover, the glucose amount in selective commercially available food samples and fresh juices was also successfully measured. The biosensor exhibits excellent selectivity, thermal stability and reproducibility. The enhanced and efficient sensitivity of the developed Au–GO based biosensor may be due to the synergic effects of the plasmonic Au-nanoparticles and GO. The performance of the biosensor suggests that the reported Au–GO hybrid nanostructures can provide a novel platform for developing non-enzymatic biosensors for biomedical and industrial applications.
关键词： hybrid nanostructures,Au–graphene oxide,non-enzymatic biosensor,electrochemical measurements,glucose sensing
更新于2025-09-16 10:30:52
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Self-Assembled Peptide Nanostructures for Photoelectrochemical Bioanalysis Application: A Proof-of-Concept Study
摘要： Currently, one of important research directions of photo-electrochemical (PEC) bioanalysis is to exploit innovative photoactive species and their elegant implementations for selective detection and signal transduction. Different from existing candidates for photoelectrode development, this study, exemplified by the cationic dipeptide nanoparticles (CDNPs), reports the first demonstration of self-assembled peptide nanostructures (SAPNs) for the PEC bioanalysis. Specifically, the CDNPs were prepared as representative materials and then immobilized onto the indium tin oxide (ITO) electrode for the PEC differentiation of several commonly involved biomolecules such as ascorbic acid (AA) and L-cysteine. Significantly, the experimental results disclosed that the CDNPs possessed unique photocathodic responses and good analytical performance toward AA detection in terms of rapid response, high stability, and excellent selectivity. This work demonstrates the great potential of the large SAPN family for the future PEC bioanalysis development and has not been reported to our knowledge.
关键词： ascorbic acid detection,photoelectrochemical bioanalysis,cationic dipeptide nanoparticles,self-assembled peptide nanostructures
更新于2025-09-16 10:30:52
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Enhanced photoresponse in ZnO nanorod array/p-GaN self-powered ultraviolet photodetectors via coupling with CuO nanostructures
摘要： ZnO nanorod arrays (ZnO NRAs) coupled with coral-like CuO nanostructures (CuO CLNs) were prepared by low-temperature hydrothermal method. Self-powered ultraviolet (UV) photodetectors (PDs) based on ZnO NRAs/CuO CLNs/p-GaN heterostructure were fabricated via a direct-contact method. Under UV illumination (1.46 mW cm?2), the ratios of photocurrent to dark current (Iphoto/Idark), photo-responsivity and speci?c detectivity for the ZnO NRAs/CuO CLNs/p-GaN heterojunction self-powered PD were estimated to be 1143, 1.44 mA W?1 and 5.9×1010 cm Hz1/2/W at 0 V, which were about ～187, ～104 and ～153 times greater than those of the ZnO NRAs/p-GaN self-powered PD, respectively. Moreover, the PD displayed faster response time, excellent stability and repeatability by coupling with CuO CLNs. The mechanism of the enhanced photoresponse performance was discussed through the energy band diagram.
关键词： self-powered,CuO nanostructures,ultraviolet photodetector,ZnO nanorods
更新于2025-09-16 10:30:52
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Monotectic growth evolution and raman scattering of self-assembled ZnO hierarchical micro-nanostructures
摘要： The self-assembled hierarchical micro-nanostructures with geometric complexity and/or constituent diversity are becoming a promising class of candidates for the next generation nanotechnology. Different from conventional vapor-liquid-solid (VLS) eutectic liquid droplets for one-dimensional (1D) nanowires, the Zn-Bi VLS monotectic liquid droplets are employed to build 1D, 2D and 3D ZnO into 3D hierarchical micro-nanostructures. As-obtained micro-nanostructures are well de?ned self-assembly and have not yet been observed in the conventional eutectic alloys. The synergy of monotectic droplets and nonthermal equilibrium is responsible for the evolution of ZnO hierarchical micro-nanostructures. Raman spectra show that E2H and E1L modes are shifted slightly towards the high-wavenumber side by an amount of 3.7 and 2 cm?1 as compared with undoped ZnO nanowires and an additional peak at 519.5 cm?1 is associated with Bi38OZn60. The results manifest that 3D ZnO micro-nanoarchitectures possess a bulk phonon structure. The monotectic liquid droplet route presented in this paper may offer a new opportunity to the fabrication of hierarchical nanostructures for realistic technology platforms with multifunctional coupling and interplay.
关键词： nanowires,growth mechanism,nanofabrications,nanostructures,Raman scattering
更新于2025-09-16 10:30:52
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Interfacial and Bulk Nanostructures Control Loss of Charges in Organic Solar Cells
摘要： Organic solar cells (OSCs) have emerged as one promising sustainable energy resource since the introduction of state-of-the-art bulk heterojunction (BHJ) device structure in early 1990s. Impressively developed molecular design methodologies in the past decade have led researchers toward utilizing more suitable pairs of low (p-type) and high (n-type) electron affinity organic semiconducting materials. Among other attributes, versatile absorption capabilities of these versatile organic materials may lead to explicit interfaces, phase distributions, and crystalline nanostructures. Structural characterization techniques involving soft and hard X-rays have enabled us to measure these morphology parameters quantitatively including their strong correlation with photovoltaic (PV) parameters. Favorable processing techniques have been adopted to realize auspicious interfacial areas and charge percolations in bulk toward efficient short circuit current (JSC) and fill factor (FF) values. Collaborative efforts in the fields of chemical structure design of materials, device characterization, and engineering have pushed the power conversion efficiencies (PCEs) of OSCs to 16%. However, the single layer BHJ structure still requires further optimizations for the extension of their PCEs toward the theoretical limit.
关键词： Organic solar cells,Photovoltaic parameters,Crystalline nanostructures,Power conversion efficiencies,Bulk heterojunction
更新于2025-09-16 10:30:52
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Probing Specificity of Protein–Protein Interactions with Chiral Plasmonic Nanostructures
摘要： Protein?protein interactions (PPIs) play a pivotal role in many biological processes. Discriminating functionally important well-defined protein?protein complexes formed by specific interactions from random aggregates produced by nonspecific interactions is therefore a critical capability. While there are many techniques which enable rapid screening of binding affinities in PPIs, there is no generic spectroscopic phenomenon which provides rapid characterization of the structure of protein?protein complexes. In this study we show that chiral plasmonic fields probe the structural order and hence the level of PPI specificity in a model antibody?antigen system. Using surface-immobilized Fab′ fragments of polyclonal rabbit IgG antibodies with high specificity for bovine serum albumin (BSA), we show that chiral plasmonic fields can discriminate between a structurally anisotropic ensemble of BSA-Fab′ complexes and random ovalbumin (OVA)-Fab′ aggregates, demonstrating their potential as the basis of a useful proteomic technology for the initial rapid high-throughput screening of PPIs.
关键词： specificity,Protein?protein interactions,structural order,chiral plasmonic nanostructures,high-throughput screening
更新于2025-09-16 10:30:52
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Plasmonic effects in the enclosed and opened metallodielectric bowtie nanostructures
摘要： Plasmonic effects in the enclosed and opened metallodielectric nanostructures, composed of a periodically bowtie-shape metal nanoparticles (MNPs), are numerically investigated and compared. The spreading range of resonance wavelength for the opened system is larger than that of the enclosed one due to more surface plasmon resonance (SPR) and hollow plasmon resonance (HPR) effects occurred in metallodielectric bowtie nanostructures. Numerical results exhibit that the sensitivity of the opened system could reach as high as 1056.60 nm/RIU. For the thinner shell thickness, it can fully support the high-energy mode with electric field concentration extended into the more dielectric core regions in the opened system, thereby provides higher sensitivity to local refractive index (RI) varies. In addition, the open hollow is accessible to the surrounding medium, and this makes it attractive for RI sensor and filtering applications. The highly sensitive optical performances give us a qualitative idea of the optical properties of SPR and HPR modes in the opened metallodielectric bowtie nanostructure system that can be as a promising candidate for analyzing the real nanocomposites and producing the nanomaterials with novel properties.
关键词： Hollow plasmon resonance,Surface plasmon resonance,Metallodielectric nanostructures,Refractive index sensor,Plasmonic effects
更新于2025-09-16 10:30:52