一种新型表面等离激元波导系统

提出了一种新型表面等离激元波导系统,并对其模式特性和对纳米微粒产生的光学力进行了研究。采用有限元软件(COMSOL)对该系统进行了数值模拟和理论分析,发现在该结构纳米级的间隙中可以形成深亚波长电磁能量的束缚。由于双波导结构之间强烈的耦合作用,相比于已有的一些表面等离激元波导,光学力至少提高了一个数量级,达到了4 200fN/W以上,同时被捕获粒子的局域范围仅有几十纳米。该波导系统可以用于强力、高精度纳米级光镊的设计和研究。     

Induced SER‐Activity in Nanostructured Ag–Silica–Au Supports via Long‐Range Plasmon Coupling

A novel Ag–silica–Au hybrid device is developed that displays a long‐range plasmon transfer of Ag to Au leading to enhanced Raman scattering of molecules largely separated from the optically excited Ag surface. A nanoscopically rough Ag surface is coated by a silica spacer of variable thickness from ～1 to 21 nm and a thin Au film of ～25 nm thickness. The outer Au surface is further functionalized by a self‐assembled monolayer (SAM) for electrostatic binding of the heme protein cytochrome c (Cyt c) that serves as a Raman probe and model enzyme. High‐quality surface‐enhanced resonance Raman (SERR) spectra are obtained with 413 nm excitation, demonstrating that the enhancement results exclusively from excitation of Ag surface plasmons. The enhancement factor is estimated to be 2 × 10⁴–8 × 10³ for a separation of Cyt c from the Ag surface by 28–47 nm, corresponding to an attenuation of the enhancement by a factor of only 2–6 compared to Cyt c adsorbed directly on a SAM‐coated Ag electrode. Upon immobilization of Cyt c on the functionalized Ag–silica–Au device, the native structure and redox properties are preserved as demonstrated by time‐ and potential‐dependent SERR spectroscopy.     

宽带RF信号光传输设备技术分析与实现

介绍了宽带RF信号直接光强度调制光发射机与光接收机的原理，分析了光传输系统中的载噪比、动态范围等重要指标。     

Controlling Surface Plasmon Optical Transmission with an Electrochemical Switch Using Conducting Polymer Thin Films

Surface plasmon resonance (SPR)‐enhanced optical transmission is actively controlled by an electrochromism of conducting polymer thin films. Polyaniline and poly(3,4‐ethylenedioxythiophene) thin films are deposited on a thin gold grating surface. SPR‐enhanced optical transmission is demonstrated by irradiating white light on the conducting polymer thin film–gold grating surface and detecting the transmitted light from the back side. The transmission SPR system is combined with an electrochemical setup to manipulate the resonance. The wavelength of the sharp peak in the transmission light spectra is tuned by electrochemical doping/dedoping of the conducting polymer thin films. The present study of controllable SPR‐enhanced optical transmission should provide novel active plasmonic devices such as active bandpass filters or biosensors.     

Cooperative Near‐Field Surface Plasmon Enhanced Quantum Dot Nanoarrays

Fluorescence from quantum dots (QDs) sandwiched between colloidal gold nanoparticles and lithographically created metal nanoarrays is studied using engineered peptides as binding agents. For optimized structures, a 15‐fold increase is observed in the brightness of the QDs due to plasmon‐enhanced fluorescence. This enhanced brightness is achieved by systematically tuning the vertical distance of the QD from the gold nanoparticles using solid‐specific peptide linkers and by optimizing the localized surface plasmon resonance by varying the geometric arrangement of the patterned gold nanoarray. The size and pitch of the patterned array affect the observed enhancement, and sandwiching the QDs between the patterned features and colloidal gold nanoparticles yields even larger enhancements due to the increase in local electromagnetic hot spots induced by the increased surface roughness. The use of bifunctional biomolecular linkers to control the formation of hot spots in sandwich structures provides new ways to fabricate hybrid nanomaterials of architecturally induced functionality for biotechnology and photonics.     

Linewidth‐Optimized Extraordinary Optical Transmission in Water with Template‐Stripped Metallic Nanohole Arrays

The experimental observation of unusually sharp plasmon resonance peaks in periodic Ag nanohole arrays made using template stripping is reported. The extraordinary optical transmission (EOT) peak associated with the surface plasmon polaritons at the smooth Ag‐water interface shows a well‐defined Fano‐type profile with a linewidth below 10 nm at a wavelength of around 700 nm. Notably, this sharp and intense radiant peak (Q factor of 71) is obtained at visible frequencies in water and at normally incident illumination. This is accomplished by obtaining high‐quality Ag surfaces with a roughness below 1 nm, which reduces the imaginary component of the Ag dielectric function that is associated with material damping, as well as shrinking the nanohole radius to decrease radiative damping of plasmons. The localized spectral response of the radiant plasmon peak is characterized using the nanohole array in water in a layer‐by‐layer fashion via sequential atomic layer deposition of Al₂O₃. Because the ultrasharp EOT peak is obtained with excellent uniformity over a centimeter‐sized area from the metallic nanohole array in water, these template‐stripped nanohole arrays will benefit many practical applications based on EOT.     

Low‐Power and High‐Contrast Nanoscale All‐Optical Diodes Via Nanocomposite Photonic Crystal Microcavities

A novel nanoscale integrated all‐optical diode is reported, realized by combining the strong plasmonic responses of gold nanoparticles with the all‐optical tunable properties of polymeric photonic crystal microcavities. Non‐reciprocal transmission properties are achieved based on the effect of surface‐plasmon resonance enhancing the optical non‐linearity and dynamic coupling of asymmetrical microcavity modes. An ultralow‐threshold photon intensity of 2.1 MW cm^?2 and an ultrahigh transmission contrast over 10⁴ are realized simultaneously. Compared with previously reported all‐optical diodes, the operating power is reduced by five orders of magnitude, while the transmission contrast is enlarged by three orders of magnitude.     

Nanoarrays: Cooperative Near‐Field Surface Plasmon Enhanced Quantum Dot Nanoarrays (Adv. Funct. Mater. 16/2010)

Fluorescence from quantum dots (QDs) sandwiched between colloidal gold nanoparticles and lithographically created metal nanoarrays is studied using engineered peptides as binding agents. For optimized structures, a 15‐fold increase is observed in the brightness of the QDs due to plasmon‐enhanced fluorescence. This enhanced brightness is achieved by systematically tuning the vertical distance of the QD from the gold nanoparticles using solid‐specific peptide linkers and by optimizing the localized surface plasmon resonance by varying the geometric arrangement of the patterned gold nanoarray. The size and pitch of the patterned array affect the observed enhancement, and sandwiching the QDs between the patterned features and colloidal gold nanoparticles yields even larger enhancements due to the increase in local electromagnetic hot spots induced by the increased surface roughness. The use of bifunctional biomolecular linkers to control the formation of hot spots in sandwich structures provides new ways to fabricate hybrid nanomaterials of architecturally induced functionality for biotechnology and photonics.     

Dynamics of Strong Coupling between J‐Aggregates and Surface Plasmon Polaritons in Subwavelength Hole Arrays

A prototypical hybrid system formed by strong coupled gold hole arrays and J‐aggregate molecules is investigated by using both steady‐state spectroscopic method and ultrafast pump‐probe approach. In particular, the plasmonic response of the device has been tuned by modifying its periodicity thus to achieve the strongest possible coupling regime. It is found that in the transient absorption spectra, under upper band excitation, the bleaching signal from uncoupled J‐aggregate molecules completely disappears. Instead, two distinctive period dependent bleaching bands are formed, clearly fingerprint of the hybrid exciton‐plasmon state. The dynamics of these bands is also directly analyzed. A remarkable long lifetime is found especially for the upper band, corresponding to the presence of a trap state in its transient absorption spectra under resonance excitation. Such unique feature should provide a new approach to control quantum‐mechanical states under coherent coupling.     

Poly[oligo(ethylene glycol) methacrylate‐co‐glycidyl methacrylate] Brush Substrate for Sensitive Surface Plasmon Resonance Imaging Protein Arrays

Surface plasmon resonance imaging (SPRi) is a unique microarray method for label‐free and multiplexed bio‐assays. However, it currently cannot be used to detect human serum samples due to its low sensitivity and poor specificity. A poly[oligo(ethylene glycol) methacrylate‐co‐glycidyl methacrylate] (POEGMA‐co‐GMA) brush was synthesized by surface‐initiated atom transfer radical polymerization (SI‐ATRP) and used as a unique supporting matrix for SPRi arrays to efficiently load probe proteins for high sensitivity while reducing nonspecific adsorptions for good selectivity. Results indicate that the polymer brush has a high protein loading capacity (1.8 protein monolayers), low non‐specific protein adsorption (below the SPR detection limit), and high immobilization stability. Three model biomarkers, α‐fetoprotein, carcinoembryonic antigen, and hepatitis B surface antigen were simultaneously detected in human serum samples by a SPRi chip for the first time, showing detection limits of 50, 20, and 100 ng mL^?1, respectively. This work demonstrates great potential for a SPRi biochip as a powerful label‐free and high‐throughput detection tool in clinical diagnosis and biological research. Since the SPR detection is limited by the sensing film thickness, this approach particularly offers a unique way to significantly improve the sensitivity in the SPR detecting thickness range.     

Surface Plasmonic‐Assisted Photocatalysis and Optoelectronic Devices with Noble Metal Nanocrystals: Design,Synthesis, and Applications

The surface plasmon resonance (SPR) of noble metals is known to improve the efficiency of various processes and devices. The photocatalytic process is the production of fuels and storage of solar photons in chemical bonds without imposing harmful threats to the environment. Photovoltaics are other devices utilizing solar energy for electrical energy. Similarly, other optoelectronic devices like photodetectors absorb photons and convert it into charges via electron–hole dissociation processes. In contrast, light‐emitting optoelectronic devices work based on the phenomenon of charge recombination to produce light. All these devices, however, have efficiency limitations, which impede the application of novel functional materials in these devices. A more direct approach is the utilization of noble metals and their complexes, which significantly enhance the efficiencies of these devices by SPR. This article highlights recent works and applications of noble metals by SPR‐enhanced photocatalysis for hydrogen evolution from water, CO₂ conversion into useful compounds, and oxidation of hazardous pollutants. In addition, the plasmon‐enhancement of optoelectronic devices is summarized. Several possible mechanisms that have been previously reported in the literature are discussed in this work, with particular emphasis on different features of these mechanisms involving devices that are not highlighted and therefore need more attention.     

Enhancement of Green Emission from InGaN/GaN Multiple Quantum Wells via Coupling to Surface Plasmons in a Two‐Dimensional Silver Array

A novel approach to enhancing the emission efficiency of InGaN/GaN multiple quantum wells via coupling to surface plasmons (SPs) in a periodic two‐dimensional silver array is demonstrated. A higher internal quantum efficiency and a higher light extraction efficiency are simultaneously achieved by engraving an array of nanoholes into the p‐GaN cladding layer, followed by partial filling with silver. By top excitation and collection from the top of the Ag‐incorporated light emitting diodes (LEDs), a 2.8‐fold enhancement in peak photoluminescence intensity is demonstrated. The proposed nanoengraving technique offers a practical approach to overcoming the limitation of the exponentially decayed SP field without sacrificing the thickness of the p‐GaN layer and to controlling the effective coupling energy. The approach is feasible for high‐power lighting applications.     

Sodium‐Ion Batteries: Building Effective Layered Cathode Materials with Long‐Term Cycling by Modifying the Surface via Sodium Phosphate

Surface stabilization of cathode materials is urgent for guaranteeing long‐term cyclability, and is important in Na cells where a corrosive Na‐based electrolyte is used. The surface of P2‐type layered Na_2/3[Ni_1/3Mn_2/3]O₂ is modified with ionic, conducting sodium phosphate (NaPO₃) nanolayers, ≈10 nm in thickness, via melt‐impregnation at 300 °C; the nanolayers are autogenously formed from the reaction of NH₄H₂PO₄ with surface sodium residues. Although the material suffers from a large anisotropic change in the c‐axis due to transformation from the P2 to O2 phase above 4 V versus Na⁺/Na, the NaPO₃‐coated Na_2/3[Ni_1/3Mn_2/3]O₂/hard carbon full cell exhibits excellent capacity retention for 300 cycles, with 73% retention. The surface NaPO₃ nanolayers positively impact the cell performance by scavenging HF and H₂O in the electrolyte, leading to less formation of byproducts on the surface of the cathodes, which lowers the cell resistance, as evidenced by X‐ray photoelectron spectroscopy and time‐of‐flight secondary‐ion mass spectroscopy. Time‐resolved in situ high‐temperature X‐ray diffraction study reveals that the NaPO₃ coating layer is delayed for decomposition to Mn₃O₄, thereby suppressing oxygen release in the highly desodiated state, enabling delay of exothermic decomposition. The findings presented herein are applicable to the development of high‐voltage cathode materials for sodium batteries.     

Biologically Enabled Syntheses of Freestanding Metallic Structures Possessing Subwavelength Pore Arrays for Extraordinary (Surface Plasmon‐Mediated) Infrared Transmission

A scalable wet chemical process has been used to convert the intricate silica microshells (frustules) of diatoms into gold structures that retained the three‐dimensional (3‐D) frustule shapes and fine patterned features. Combined use of an amine‐enriching surface functionalization protocol and electroless deposition yielded thin (<100 nm) conformal nanocrystalline gold coatings that, upon selective silica dissolution, were converted into freestanding gold structures with frustule‐derived 3‐D morphologies. By selecting a diatom frustule template with a quasi‐regular hexagonal pore pattern (Coscinodiscus asteromphalus, CA), gold replica structures possessing such pore patterns were produced that exhibited infrared transmission maxima/reflection minima that were not observed for the starting silica diatom frustules or for flat nonporous gold films; that is, such extraordinary optical transmission (EOT) resulted from the combined effects of the quasi‐periodic hexagonal hole structure (inherited from the CA diatom frustules) and the gold chemistry. Calculated and measured IR transmission spectra obtained from planar gold films with quasi‐periodic hexagonal CA‐derived hole patterns, or with short‐range periodic hexagonal hole patterns, indicated that the enhanced IR transmission exhibited by the gold CA frustule replicas was enabled by the generation and transmission of surface plasmons. This scalable bio‐enabled process provides a new and attractive capability for fabricating self‐supporting, responsive, 3‐D metallic structures for use as dispersible/harvestable microparticles tailored for EOT‐based applications.     

Investigation of Optical and Structural Stability of Localized Surface Plasmon Mediated Light‐Emitting Diodes by Ag and Ag/SiO2 Nanoparticles

Localized surface plasmon (LSP) effects due to Ag and Ag/SiO₂ nanoparticles (NPs) deposited on GaN/InGaN multiquantum well (MQW) light‐emitting diode (LED) structures are studied. The colloidal NPs are synthesized by a sol‐gel method and drop‐cased on the LED structures. The surface density of NPs its controlled by the concentration of the NP solution. Theoretical modeling is performed for the emission spectrum and the electric field distribution of LSP resonance for Ag/SiO₂ NPs. Enhanced photoluminescence (PL) efficiency is observed in the LED structures and the amount of PL enhancement increases with increasing the surface density of Ag and Ag/SiO₂ NPs. These effects are attributed to resonance coupling between the MQW and LSP in the NPs. It is also shown that the PL enhancement attainable with Ag NPs and Ag/SiO₂ NPs is comparable, but the latter displays a much higher stability with respect to long‐term storage and annealing due to a barrier for NP agglomeration, Ag oxidation, and impurity diffusion provided by the SiO₂ shell.     

Chromatic Dispersion Compensation via Mid‐span Spectral Inversion with Periodically Poled LiNbO3 Wavelength Converter at Low Pump Power

Mid‐span spectral inversion (MSSI) has to utilize high optical pump power, for its operation principle is based on a nonlinear optical wavelength conversion. In this paper, a low pump‐power operation of MSSI‐based chromatic dispersion compensation (CDC) has been achieved successfully, for the first time to our knowledge, by introducing a noise pre‐reduction scheme in cascaded wavelength conversions with periodically poled LiNbO₃ waveguides at a relatively low operation temperature. As preliminary studies, phase‐matching properties and operation‐temperature dependence of the wavelength converter (WC) were characterized. The WC pumped at 1549 nm exhibited a wide conversion bandwidth of 59 nm covering the entire C‐band and a conversion efficiency of –23.6 dB at 11 dBm pump power. CDC experiments were implemented with 2.5 and 10 Gb/s transmission systems over 100 km single‐mode fiber. Although it is well‐known that the signal distortion due to chromatic dispersion is not critical at a 2.5 Gb/s transmission, the clear recovery of eye patterns was identified. At 10 Gb/s transmission experiments, eye patterns were retrieved distinctly from seriously distorted ones, and notable improvements in bit‐error rates were acquired at a low pump power of 14 dBm.