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Plasmonic Effects of Dual-Metal Nanoparticle Layers for High-Performance Quantum Dot Solar Cells
摘要： To improve quantum dot solar cell performance, it is crucial to make efficient use of the available incident sunlight to ensure that the absorption is maximized. The ability of metal nanoparticles to concentrate incident sunlight via plasmon resonance can enhance the overall absorption of photovoltaic cells due to the strong confinement that results from near-field coupling or far-field scattering plasmonic effects. Therefore, to simultaneously and synergistically utilize both plasmonic effects, the placement of different plasmonic nanostructures at the appropriate locations in the device structure is also critical. Here, we introduce two different plasmonic nanoparticles, Au and Ag, to a colloidal PbS quantum dot heterojunction at the top and bottom interface of the electrodes for further improvement of the absorption in the visible and near-infrared spectral regions. The Ag nanoparticles exhibit strong scattering whereas the Au nanoparticles exhibit an intense optical effect in the wavelength region where the absorption of light of the PbS quantum dot is strongest. It is found that these dual-plasmon layers provide significantly improved short-circuit current and power conversion efficiency without any form of trade-off in terms of the fill factor and open-circuit voltage, which may result from the indirect contact between the plasmonic nanoparticles and colloidal quantum dot films.
关键词： Quantum dot solar cell,Plasmonic effect,Near-field oscillation,Colloidal quantum dot,Light scattering
更新于2025-09-16 10:30:52
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[IEEE 2019 Antenna Measurement Techniques Association Symposium (AMTA) - San Diego, CA, USA (2019.10.6-2019.10.11)] 2019 Antenna Measurement Techniques Association Symposium (AMTA) - Waveguide-integrated Rydberg Atom-based RF Field Detector for Near-field Antenna Measurements
摘要： We demonstrate simultaneous amplitude and phase measurements of a radio-frequency (RF) ?eld through the use of a Rydberg atom-based sensor embedded inside a waveguiding structure. This measurement uses the Rydberg atom-based sensor in a mixer con?guration, which requires the presence of a local oscillator (LO) RF ?eld. The waveguiding structure supplies the LO ?eld. The combined waveguide and Rydberg atom system is used to measure phase and amplitude in the near-?eld of a horn antenna to extract the far-?eld pattern.
关键词： far-field pattern,near-field antenna measurements,waveguide,Rydberg atom-based sensor,RF field measurements
更新于2025-09-12 10:27:22
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Scanning laser terahertz near-field reflection imaging system
摘要： We developed a scanning laser terahertz (THz) near-field reflection imaging system using a fiber-coupled femtosecond laser source for high spatial resolution measurements without any sub-wavelength probes. In this system, THz wave pulses generated at the laser focusing spot in a non-linear optical crystal interact with a sample set on the crystal. Using this system, we obtained the THz reflection images of metallic structures with a resolution of ～λTHz/34 (λTHz = 680 μm) and also observed paraffin-embedded human breast tissue of several 10 μm in size. These results promise that this system can be suitable for industrial applications which require micron-scale resolution.
关键词： near-field,terahertz,reflection imaging,femtosecond laser,high spatial resolution
更新于2025-09-12 10:27:22
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Effect of plasmonic lens distribution on flight characteristics in rotational near-field photolithography
摘要： Rotational near-?eld photolithography exposes photoresists by exciting surface plasmon polaritons to realize nanopatterns with ultrahigh-resolution beyond the di?raction limit. This feature enables broad application prospects in the micro-nanomanufacturing ?eld. The lithography ?ight head, carrying a plasmonic lens (PL), with an approximately 10 nm spacer from the substrate, is the core of the system for e?ective etching. This paper investigates the ?ight state of a PL-loaded lithography head on the air ?lm, based on computational ?uid dynamics analysis. We found that the in?uence of the PL on the ?ight height produces an edge e?ect. This means that a PL fabricated on the edge region can signi?cantly a?ect the ?ight height of the head. By processing the PL at a distance of 10 μm from the edge of the slider tail block, a steady 37 nm linewidth depth pattern was ?nally realized, using a rotational near-?eld photolithography system.
关键词： edge effect,rotational near-field photolithography,flight characteristics,plasmonic lens,computational fluid dynamics
更新于2025-09-12 10:27:22
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Broadband Plasmonic Enhancement of High-Efficiency Dye-Sensitized Solar Cells by Incorporating Au@Ag@SiO <sub/>2</sub> Core–Shell Nanocuboids
摘要： The introduction of plasmonic additives is a promising approach to boost the efficiency of dye-sensitized solar cell (DSSC) since it may improve the light harvesting of a solar cell. Herein, we design broadband and strong plasmonic absorption Au@Ag@SiO2 nanocuboids (GSS NCs) as nanophotonic inclusions to achieve plasmon-enhanced DSSCs. These multiple resonances absorption arising from GSS NCs can be readily adjusted by altering their structures to complementarily match the absorption spectrum of the dyes, especially in weak absorption zones. By subtly regulating the position of nanophotonic inclusions in the photoanodes, not only the plasmonic near-field enhancement but also far-field light-scattering could be adequately developed to promote the light harvest and thus the efficiency of DSSCs. The resulting solar cells yield an average efficiency of 10.34%, with a champion value of 10.58%. The electromagnetic simulations are consistent with the experimental observations, further corroborating the synergistic effect of plasmonics improvement in these DSSCs.
关键词： near-field effect,light-scattering,light management,plasmon resonance,dye-sensitized solar cells
更新于2025-09-12 10:27:22
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Near‐field analysis of discrete bowtie plasmonic nanoantennas
摘要： A discrete antenna is a discretized version of a traditional antenna design which enhances the antenna properties (such as field intensity, multi-band, compact size, and low sidelobe levels) of its traditional counterpart. In this work, a classical bowtie antenna is discretized using circular elements of different sizes. Numerical simulations and near-field optical scanning microscopy are performed on classical and discrete bowtie antennas in the infrared. Simulations show that discrete antennas have an increased bandwidth and an increased number of electric-field hot-spots and near-field measurements confirm the increment of hotspots. These characteristics make discrete antennas potentially useful in applications where an extended region of localized electric field enhancements is of interest.
关键词： discrete bowtie,scanning-scattering near-field optical microscopy,plasmonic nanoantenna
更新于2025-09-11 14:15:04
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - The terahertz near-field response of graphene layers and graphene structures
摘要： We report on the experimental study of the scattering and the near-field interaction of a THz electromagnetic field with graphene layers near the probe of a terahertz near-field microscope. There are resonance lines in the spectrum for a graphene monolayer-based transistor structure, which is possibly due to the strong plasmon response at terahertz frequencies and the manifestation of plasmon interference in the graphene strip.
关键词： terahertz,near-field microscopy,graphene,plasmon response
更新于2025-09-11 14:15:04
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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) - Antenna Tapering Strategy for Near-Field Enhancement Optimization in Terahertz Gold Nanocavities
摘要： Plasmonic nanoantennas (NAs) have received a growing attention in recent years due to their ability to confine light on sub-wavelength dimensions. More recently, this property has been exploited in the terahertz (THz) frequency range (0.1-10 THz) for enhanced sensing and spectroscopy, as well as for more fundamental investigations. These applications typically require high local electric fields that can be achieved by concentrating THz radiation into deeply sub-wavelength volumes located at the NAs extremities. However, the achievable near-field enhancement values are severely limited by the poor resonance quality factor of traditional rod-shaped THz NAs. Unlike what is commonly assumed in the infrared domain, here we show that an optimal NA tapering angle can be effectively introduced to obtain higher quality factors and, at least, twofold higher local near-field enhancement in comparison with standard (wire-like) dipolar THz NAs. To evaluate how the tapering angle affects the NA performance, a simplified quasi-analytical model was first developed. Each NA is considered as a truncated cone constituted by a sequence of gold cylinders of increasing radii, so that the effective refractive index of the surface mode propagating along the NA changes gradually along the main axis. Once the reflection coefficients for the surface mode at both extremities are retrieved, a NA can be interpreted as a Fabry-Perot resonator and its resonances can be analytically calculated. This model reveals a trade-off between large tapering angles (resulting in a low reflection coefficient at the large extremity) compared to small tapers (which are affected by high propagation losses for the surface mode), leading to an optimal taper angle. FEM-based simulations (COMSOL Multiphysics) were then used to confirm this prediction. 60-nm-thick gold tapered NA dimers were designed with 45-μm-long arms (in order to resonate at around 1 THz) and with their facing tips (100-nm-wide) separated by a 30 nm gap, thus realizing a bowtie geometry. We numerically investigated the near-field enhancement in the gap between the NAs, varying the tapering angle α from 0° to 10°. We found that in planar gold NA dimers the near field grows as the tapering angle increases up to α = 3.4°, where the maximum is reached. In order to experimentally confirm these results, arrays of gold tapered NA dimers were fabricated by electron beam lithography on a high resistivity silicon substrate. A transmission characterization by means of THz time-domain (far-field) spectroscopy was then carried out on the fabricated NA arrays revealing, as expected, an increase of the resonance quality factor for the optimized tapered geometry. In conclusion, we demonstrated an effective, yet simple, way to further boost and engineer the local field enhancement of THz NAs.
关键词： Plasmonic nanoantennas,tapering angle,near-field enhancement,quality factor,terahertz
更新于2025-09-11 14:15:04
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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) - Determining the Waveguide Profile using the Overlap Integral
摘要： The determination of the index pro?le in guiding structures is a central problem in applied photonics, ranging from optical ?bers to femtosecond-written waveguides. A non-destructive and relatively easy method consists in the measurement of the index pro?le by measuring the transmitted ?eld. From the transmitted ?eld, the refractive index pro?le is computed by direct inversion of the Helmholtz equation. This technique is called near-?eld method. Here we present a new near-?eld method based upon the inversion of the overlap integral. From the waveguide theory, the power coupled to the m-th mode with pro?le ψm(x) from an input Ein(x) is am = (cid:2) Ein(x)ψ ? (x)dx. If the input Ein(x) is shifted by an amount x0, the overlap am(x0) is the convolution between the pro?le of the input beam Ein and the mode pro?le ψm. The convolution operator implicitly ?lters out the noise, but without creating distorsions or artifacts. An experimental measurement of the transmitted ?eld Eexp will be Nη, where η is a white Gaussian noise and N the noise amplitude. In the previous formulae P is the overall power given by |am(x0)|2. If both amplitude and phase of the transmitted ?eld are simultaneously measured, the overlap am can be inverted for any guided mode m. If only the intensity is measured, the overlap can be inverted only if the waveguide is monomodal. An example of the reconstructed mode in the case of intensity-only measurements is plotted in Fig. 1(a) for ψ0 = cosh(x/w) with w/λ = 4 and N/P = 1 × 10?4. The retrieved ?eld is very close to the exact one, with appreciable differences only for |x/λ | > 10. Important to stress, this range is larger than what it is achievable with a single direct measurement of the transmitted ?eld. The next step is to invert the Helmholtz equation, that is, to compute the second derivative of the retrieved mode. Direct application of the inversion protocol strongly enhances the noise, above all on the tails of the mode. The net result is the appearance of several fake oscillations, even where the retrieval of the mode is good. The problem can be overcome by ?tting the mode tails with a decaying exponential, in accordance with the waveguide theory. The reconstructed guide pro?les shown in Fig. 1(b) do not present arti?cial oscillations on the tails, showing a 10% error with respect to the original waveguide, the error depending slightly on the original signal-to-noise ratio N/P.
关键词： refractive index,overlap integral,Helmholtz equation,waveguide profile,near-field method
更新于2025-09-11 14:15:04
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Enhanced photo-sensitivity in a Si photodetector using a near-field assisted excitation
摘要： Silicon is an indispensable material in electric device technology. However, Si is an indirect bandgap material; therefore, its excitation efficiency, which requires phonon assistance, is low under propagating far-field light. To improve the excitation efficiency, herein we performed optical near-field excitation, which is confined in a nano-scale, where the interband transitions between different wave numbers are excited according to the uncertainty principle; thus, optical near-field can directly excite the carrier in the indirect bandgap. To evaluate the effect of optical near-field confined in a nano-scale, we fabricate the lateral Si p–n junction with Au nanoparticles as sources to generate the field confinement. We observed a 47.0% increase in the photo-sensitivity rate. In addition, by using the thin lateral p–n junction, which eliminates the far-field excitation, we confirmed a 42.3% increase in the photo-sensitivity rate.
关键词： optical near-field,Au nanoparticles,photo-sensitivity,Silicon,photodetector
更新于2025-09-11 14:15:04