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Plasmonic Nanocavity Metasurface Based on Laser-Structured Silver Surface and Silver Nanoprisms for the Enhancement of Adenosine Nucleotide Photoluminescence
摘要： A reliable photoluminescence (PL) spectroscopy and imaging of biomolecules at room temperature is a challenging and important problem of biophysics, biochemistry, and molecular genetics. A unique effect of strong plasmonic enhancement of the PL by metal nanostructures is one of the most effective approaches for this purpose. The highest enhancement is provided by metal nanostructures with densely packed sharp tips, periodically arranged metal nanostructures, and plasmonic cavities. All of these features have been realized in the plasmonic cavity metasurface based on the silver (Ag) laser-induced periodic surface structure and Ag triangular nanoprisms studied in the present work. The strong plasmon-enhanced PL of 5′-deoxyadenosine monophosphate deposited on such metasurfaces has been revealed at room temperature. The observed enhancement of more than 1000-fold has been interpreted as a result of synergetic action of the generation of a high concentration of hot spots near the sharp edges of the laser-induced surface structure and nanoprisms together with excitation of the collective gap mode of the cavity due to strong near-field plasmonic coupling. Correspondingly, the plasmonic cavity metasurfaces consisting of metal laser-induced periodic surface structures and nonspherical metal nanoparticles with sharp edges have been shown to be crucial for the highly sensitive detection and imaging of biomolecules at room temperature without consuming any dye labels.
关键词： hot spots,plasmon gap mode,plasmonic metasurface,near-field coupling,nucleotide photoluminescence enhancement
更新于2025-11-19 16:46:39
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Planar plasmonic nanocavity for efficient enhancement of photoluminescence of molecular emitters
摘要： Effects of plasmonic gap mode formation due to coupling between metal nanoparticles and thin metal film separated by thin dielectric luminescent film-spacer (gap) have been studied by means of light extinction and photoluminescence in three-layer planar Au NPs monolayer/shellac-dye film/Au film nanostructure with spacer thickness varied in the range 8–47 nm. The 3-fold enhancement of light extinction and 90 nm red shift of the plasmon mode have been observed in extinction spectra. The 37-fold enhancement of dye photoluminescence and the significant (48 nm) red shift of dye photoluminescence band have been observed for Au NPs monolayer/shellac-dye film/Au film nanostructure in comparison with bare shellac-dye film for the spacer thickness of 8 nm. The decrease of the spacer thickness causes the increase of the enhancement factor of dye photoluminescence indicating the strengthening of the gap mode field. FDTD calculations of the dependence of the intensity of the field of gap mode on the gap thickness have demonstrated good quantitative agreement with experimental data that proves the key role of gap mode in the enhancement of the electromagnetic field in planar metal NPs monolayer/dielectric film/metal film plasmonic nanocavity nanostructures. The variation of the gap thickness provides the possibility to tune controllably the spectral position and enhancement factor of the light emission from the molecular emitters located in the gap that can be used in the novel nanophotonics devices and for highly sensitive detection of the single molecules.
关键词： Near field coupling,Gap thickness dependence,Molecular emitters,Gap mode,Plasmonic nanocavity,Photoluminescence enhancement
更新于2025-11-19 16:46:39
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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 URSI Asia-Pacific Radio Science Conference (AP-RASC) - New Delhi, India (2019.3.9-2019.3.15)] 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - Near-field vertical coupling between terahertz photonic crystal waveguides
摘要： We demonstrate near-field coupling between terahertz photonic crystal waveguides in the out-of-plane dimension, with no direct physical contact, by making use of coupled-line techniques. Efficient transfer (i.e. ≈ 80%) of terahertz power from one waveguide to another is experimentally achieved. Thereafter, multi-Gbps data is successfully transmitted via this near-field link. This study can be considered a step towards practical connectors between terahertz photonic crystal waveguide circuits.
关键词： near-field coupling,photonic crystal waveguides,multi-Gbps data transmission,terahertz,coupled-line techniques
更新于2025-09-11 14:15:04
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UHF Reader Antenna for Near and Far-Field RFID Operation
摘要： In order to detect the RFID tags kept inside an enclosure, the reader antenna can couple energy into another antenna kept in the near-field region. To detect the tags placed in the far-field, the reader antenna should have a good gain. Usually, these two requirements compete with each other due to the effect of coupling on the frequency of operation of the antenna system. In this work modification to a loop antenna is proposed such that it can operate in both near and far-field. Loop antenna with high impedance surface (HIS) reflector results in a low-profile antenna pair where both the antennas can interchangeably operate in near-field and far-field, with their operating frequency band independent of the spacing between the antennas. The performance of the proposed antennas is compared with that of several other antennas by measuring the read range of RFID tags. It is found that the proposed antennas perform better in comparison with the other antennas when detecting the tags placed inside an enclosure. When operating as a far-field antenna, their performance is very close to that of a conventional RFID reader antenna which is optimized only for far-field operation.
关键词： near-field coupling,far-field near-field antenna,RFID,UHF,high impedance surface,loop antennas
更新于2025-09-04 15:30:14