Plasmonic sensor with self-reference capability based on functional layer film composed of Au/Si gratings

We propose a simple one-dimensional grating coupling system that can excite multiple surface plasmon resonances for refractive index(RI)sensing with self-reference characteristics in the near-infrared band.Using theoretical analysis and the finite-difference time-domain method,the plasmonic mechanism of the structure is discussed in detail.The results show that the excited resonances are independent of each other and have different fields of action.The mode involving extensive interaction with the analyte environment achieves a high sensitivity of 1236 nm/RIU,and the figure of merit(FOM)can reach 145 RIU-1.Importantly,the mode that is insensitive to the analyte environment exhibits good self-reference characteristics.Moreover,we discuss the case of exchanging the substrate material with the analyte environment.Promising simulation results show that this RI sensor can be widely deployed in unstable and complicated environments.     

Plasmonic refractive index sensor based on the combination of rectangular and circular resonators including baffles

We numerically designed a plasmonic refractive index sensor with high sensitivity and tunable optical feature based on two metal-insulator-metal bus waveguides connecting with the central-coupled rectangular and circular ring resonators, including silver (Ag) baffles. In the design process, Ag baffles' influence on transmittance spectrum, magnetic and electric field distributions, surface power flow intensity, energy streamlines, and sensor performance are investigated using the finite element method. The proposed structure can use as a high precision plasmonic refractive index sensor for refractive index in the increment range of 0.01. The maximum sensitivity can reach 3400 nm/RIU (RIU is a refractive index unit), which remarkably increases the sensitivity of 1.36 times compared to the case without Ag baffles. Besides, the figure of merit and quality factor can achieve 36.00 and 42.28, respectively. The sensitivity and figure of merit can be increased by adding the Ag baffles in the proposed plasmonic sensor system, generating an additional gap plasmon resonance mode that cannot find in a typical case.     

Effects of thickness & shape on localized surface plasmon resonance of sexfoil nanoparticles

Localized surface plasmon(LSPR) resonance and sensing properties of a novel nanostructure(sexfoil nanoparticle)are studied using the finite-difference time-domain method. For the sandwich sexfoil nanoparticle, the calculated extinction spectrum shows that with the thickness of the dielectric layer increasing, long-wavelength peaks blueshift, while shortwavelength peaks redshift. Strong near-field coupling of the upper and lower metal layers leads to electric and magnetic field resonances; as the thickness increases, the electric field resonance gradually increases, while the magnetic field resonance decreases. The obtained refractive index sensitivity and figure of merit are 332 nm/RIU and 3.91 RIU~(-1), respectively. In order to obtain better sensing ability, we further research the LSPR character of monolayer Ag sexfoil nanoparticle. After a series of trials to optimize the thickness and shape, the refractive index sensitivity approximates 668 nm/RIU, and the greatest figure of merit value comes to 14.8 RIU~(-1).     

多孔钛酸钡陶瓷制备及其增强的压电灵敏性

在压电陶瓷中增加孔洞数量,可以有效改善陶瓷的静水压优值,提高其压电灵敏性.考虑到铅基压电陶瓷对环境和人体的危害,本文以糊精为造孔剂,采用传统固相烧结法制备无铅钛酸钡(BaTiO_3)多孔压电陶瓷.研究烧结温度(1250,1280,1300℃)和糊精含量(5%,10%,15%)对BaTiO_3陶瓷晶体结构、孔隙率以及孔形貌特征的影响,探索孔隙率与BaTiO_3陶瓷介电、压电、声阻抗以及静水压优值等性能之间的相关性.结果表明:所有多孔陶瓷表现出三维贯通的开气孔,尺寸约为1—7μm.烧结温度强烈影响BaTiO_3陶瓷的孔隙率,加入10%低沸点的糊精时,1250℃和1280℃烧结均获得孔隙率高达58%的多孔BaTiO_3陶瓷;然而1300℃烧结,陶瓷孔隙率急速下降到13%.1250℃烧结10%糊精含量的陶瓷表现出高的静水压优值(约8376×10~/(-15)Pa~(-1))和低的声阻抗(约2.84MRrayls(1Rayl=10Pa·s/m)).与1250℃相比,1280℃烧结的陶瓷晶粒之间的结合力明显增强,有利于提高陶瓷的力学强度.这些优异的性能预示着多孔钛酸钡陶瓷在传感器和水听器领域有着潜在的应用前景.     

含双挡板金属-电介质-金属波导耦合方形腔的独立调谐双重Fano共振特性

基于表面等离子激元在亚波长结构的传输特性,设计了一种含双挡板金属-电介质-金属波导耦合两个方形腔的结构.由F-P谐振腔产生的宽谱模式与两个方形谐振腔产生的两个窄谱模式发生干涉作用,形成了独立调谐的双重Fano共振,而且可以通过改变两个方形腔的大小及填充介质实现双重Fano共振的独立调谐.基于耦合模理论,定性分析了该结构产生双重Fano共振的机理.利用有限元仿真的方法,定量分析了结构参数对可独立调谐双重Fano共振和折射率传感特性的影响.结果表明,优化参数后该结构的灵敏度分别高达1020和1120 nm/RIU, FOM值分别高达3.59×10~5和1.17×10~6.该结构可为超快光开关、多功能高灵敏度传感器和慢光器件的光学集成提供有效的理论参考.     

All polymer asymmetric Mach-Zehnder interferometer waveguide sensor by imprinting bonding and laser polishing

We present an all polymer asymmetric Mach–Zehnder interferometer(AMZI) waveguide sensor based on imprinting bonding and laser polishing method. The fabrication methods are compatible with high accuracy waveguide sensing structure. The rectangle waveguide structure of this sensor has three sensing surfaces contacting the test media, and its sensing accuracy can be increased 5 times compared with that of one surface sensing structure. An AMZI device structure is designed. The single mode condition, the length of the sensing arm, and the length deviation between the sensing arm and the reference arm are optimized. The length deviation is optimized to be 19.8 μm in a refractive index range between1.470 and 1.545. We fabricate the AMZI waveguide by lithography and wet etching method. The imprinting bonding and laser polishing method is proposed and investigated. The insertion loss is between-80.36 dB and-10.63 dB. The average and linear sensitivity are 768.1 d B/RIU and 548.95 dB/RIU, respectively. And the average and linear detection resolution of the sensor are 1.30×10~(-6) RIU(RIU: refractive index unit) and 1.82×10~(-5) RIU, respectively. This sensor has a fast and cost-effective fabrication process which can be used in the cases of requiring portability and disposability.     

Design and optimization of nano-column array based surface plasmon resonance sensor

In this paper, a surface plasmon resonance fiber sensor based on gold nano-column array instead of gold film is designed and optimized. The finite element method is used to optimize the diameter of the nano-gold column under the consideration of figure of merit, which relates to the sensitivity, resonance wavelength and resonance intensity. The optimized sensor has 70 nm gold nano-column coated on a side polished single mode fiber. The results show that the average sensitivity reaches 5318 nm/RIU when the environmental refractive index changing from 1.33 to 1.39 RIU, which is much higher than those in the conventional surface plasmon resonance structure. The optimizes design will serve a vital foundation to the fabrication of high performance fiber optic surface plasmon resonance sensors based on nano metallic structure.     

Numerical study of a highly sensitive surface plasmon resonance sensor based on circular-lattice holey fiber

A new design of surface plasmon resonance (SPR) sensor employing circular-lattice holey fiber to achieve high-sensitivity detection is proposed. The sensing performance of the proposed sensor is numerically investigated and the results indicate that our proposed SPR sensor can be applied to the near-mid infrared detection. Moreover, the maximum wavelength sensitivity of our proposed sensor can reach as high as 1.76×10⁴ nm/refractive index unit (RIU) and the maximum wavelength interrogation resolution can be up to 5.68×10^-6 RIU when the refractive index (RI) of analyte lies in (1.31, 1.36). Thanks to its excellent sensing performance, our proposed SPR sensor will have great potential applications for biological analytes detection, food safety control, bio-molecules detection and so on.     

基于表面等离子体共振的新型超宽带微结构光纤传感器研究

基于表面等离子体共振的微结构光纤传感器具有高灵敏、免标记和实时监控等优点.如今,由于此类传感器广泛应用于食品安全控制、环境检测、生物分子分析物检测等诸多领域而受到大量研究.然而,目前所报道的绝大多数此类传感器只能应用于可见光或近中红外传感.因此,对可应用于中红外传感的表面等离子体共振微结构光纤传感器的研究是一项极具挑战性的工作.基于此,本文设计了一种可以工作在近红外和中红外区域的新型高灵敏表面等离子体共振微结构光纤传感器.传感器采用双芯单样品通道结构,该结构不仅可以消除相邻样品通道间的相互干扰和提高传感器的信噪比,还可以在超宽带波长范围内实现高灵敏检测.采用全矢量有限元法对其传感特性进行了系统的研究,研究结果表明:当待测样品折射率分布在1.423—1.513范围内时,传感器不仅可以在1.548—2.796μm的超宽带波长范围内进行工作,而且其平均灵敏度高达13964 nm/RIU.此外,传感器的最高波长灵敏度和折射率分辨率分别为17900 nm/RIU,5.59×10^–7 RIU.     

Design of a highly sensitive surface plasmon resonance sensor using aluminum-based diffraction grating

A highly-sensitive grating-based surface plasmon resonance (SPR) sensor is proposed. The angular interrogation method has been used to study the performance of the sensor, and high sensitivity is obtained if the ?1st diffraction order is used to excite surface plasmon (SP). The sensitivity as well as the width of the SPR curves and reflective amplitude is considered for designing the sensor. Compared with the conventional gold (Au)-based or silver (Ag)-based SPR sensor, it is found that the aluminum (Al)-based sensor has the best performance. The oxidation problem of an Al-based SPR sensor has been addressed by coating it with an ultrathin gold film on the surface. Numerical simulations based on rigorous coupled wave analysis (RCWA) show that the sensitivity of the optimized sensor is 245°/RIU (degree per refractive index unit).     

Novel high-K with low specific on-resistance high voltage lateral double-diffused MOSFET

A novel voltage-withstand substrate with high-K (HK, k>3.9, k is the relative permittivity) dielectric and low specific on-resistance (R_on,sp) bulk-silicon, high-voltage LDMOS (HKLR LDMOS) is proposed in this paper. The high-K dielectric and highly doped interface N⁺-layer are made in bulk silicon to reduce the surface field drift region. The high-K dielectric can fully assist in depleting the drift region to increase the drift doping concentration (N_d) and reshape the electric field distribution. The highly doped N⁺-layer under the high-K dielectric acts as a low resistance path to reduce the R_on,sp. The new device with the high breakdown voltage (BV), the low R_on,sp, and the excellent figure of merit (FOM=BV²/R_on,sp) is obtained. The BV of HKLR LDMOS is 534 V, R_on,sp is 70.6 mΩ·cm², and FOM is 4.039 MW·cm^-2.     

准晶体结构光纤表面等离子体共振传感器特性研究

光纤表面等离子体共振传感器在高灵敏度传感和在线实时监测等领域具有重要意义. 设计了一种六重准晶体结构环形通道光纤表面等离子体共振传感器, 基于有限元法对该传感器的传感特性进行了数值模拟. 研究了光纤各结构参量对传感器特性的影响规律. 研究结果表明: 待测液折射率的有效监测范围为1.25–1.331, 最高灵敏度可达26400 nm·RIU^-1, 传感器具有损耗谱杂峰少、探测范围广、灵敏度高、设计灵活性高和光路可弯曲等特点, 在生化检测、公共安全、环境污染监测以及高灵敏度传感等领域具有广泛的应用前景.     

Novel high-quality Fano resonance based on metal-insulator-metal waveguide with L-shaped resonators

Developing a convenient method that can be routinely applied for ascertaining proportions of different vegetable oils employed in commercial blended edible oils remains a significant challenge. We address this issue by proposing a novel method for detecting volume fraction of different oils based on the fact that these oils are optically transparent and have slightly different indices of refraction at a given temperature and wavelength. Accordingly, we develop a highly sensitive sensor for measuring the index of refraction of oil blends based on Fano resonance spectra obtained using a metal-insulatormetal(MIM) waveguide structure comprising a gapped straight waveguide coupled with two L-shaped resonators. The index of refraction sensitivity and figure of merit of the structure are calculated based on modeling using the finite element method, and the waveguide structure is accordingly optimized by adjusting the different geometric parameters to achieve a high-quality Fano resonance spectrum. The optimized structure achieves an ultra-high refractive index sensitivity of 770 nm/RIU in terms of a refractive index unit(RIU) of 1. Moreover, a highly stable linear relationship is obtained between the refractive index of mixed edible oils and the resonance wavelength. Experimental results demonstrate that the proposed structure can detect slight changes in the volume fractions of the components in blended oils.     

Design and simulation of AlN-based vertical Schottky barrier diodes

The key parameters of vertical AlN Schottky barrier diodes(SBDs) with variable drift layer thickness(DLT) and drift layer concentration(DLC) are investigated. The specific on-resistance(R_(on,sp)) decreased to 0.5 m? · cm~2 and the breakdown voltage(V_(BR)) decreased from 3.4 kV to 1.1 kV by changing the DLC from 10~(15) cm~(-3) to 3×10~(16) cm~(-3). The VBRincreases from 1.5 kV to 3.4 kV and the Ron,sp also increases to 12.64 m? · cm~2 by increasing DLT from 4-μm to 11-μm. The VBRenhancement results from the increase of depletion region extension. The Baliga's figure of merit(BFOM) of3.8 GW/cm~2 was obtained in the structure of 11-μm DLT and 10~(16) cm~(-3) DLC without FP. When DLT or DLC is variable,the consideration of the value of BFOM is essential. In this paper, we also present the vertical AlN SBD with a field plate(FP), which decreases the crowding of electric field in electrode edge. All the key parameters were optimized by simulating based on Silvaco-ATLAS.     

A high figure of merit localized surface plasmon sensor based on a gold nanograting on the top of a gold planar film

We investigate the sensitivity and figure of merit （FOM） of a localized surface plasmon （LSP） sensor with gold nanograting on the top of planar metallic film. The sensitivity of the localized surface plasmon sensor is 317 nm/RIU, and the FOM is predicted to be above 8, which is very high for a localized surface plasmon sensor. By employing the rigorous coupled-wave analysis （RCWA） method, we analyze the distribution of the magnetic field and find that the sensing property of our proposed system is attributed to the interactions between the localized surface plasmon around the gold nanostrips and the surface plasmon polarition on the surface of the gold planar metallic film. These findings are important for developing high FOM localized surface plasmon sensors.     

A theoretical study of a plasmonic sensor comprising a gold nano-disk array on gold film with a SiO_2 spacer

A plasmonic refractive index(RI) sensor with high RI sensitivity based on a gold composite structure is proposed.This composite structure is constructed from a perfect gold nano-disk square array on a gold film, with a SiO_2 spacer. The reflection spectra of the composite structure, with analyte RI in the range of 1.30 to 1.40, are theoretically studied using the finite-difference time-domain method. The incident light beam is partly coupled to the localized surface plasmons(LSP) of the single nano-disks and partly transferred to the propagating surface plasmons(PSP) by grating coupling. The reflectivity is nearly zero at the valley of the reflection spectrum because of the strong coupling between LSP and PSP. Also, the full width at half maximum(FWHM) of one of the surface plasmon polaritons(SPPs) modes is very narrow, which is helpful for RI sensing. An RI sensitivity as high as 853 nm/RIU is obtained. The influence of the structure parameters on the RI sensitivity and the sensor figure of merit(FOM) are investigated in detail. We find that the sensor maintains high RI sensitivity over a large range of periods and nano-disk diameters. Results of the theoretical simulation of the composite structure as a plasmonic sensor are promising. Thus, this composite structure could be extensively applied in the fields of biology and chemistry.     

工字形太赫兹超材料吸波体的传感特性研究

利用超材料吸波体对材料参数的电磁响应, 可将其应用于传感. 本文设计了一种工字形单元结构的超材料吸波体, 基于频域算法对其在太赫兹频段的传感特性进行数值模拟, 研究了待测样品折射率、厚度及电介质隔层厚度对超材料吸波体传感器的频率灵敏度、振幅灵敏度及品质因数的影响. 研究结果表明:当待测样品厚度为40 μm时, 折射率频率灵敏度可达到153.17 GHz/RIU, 折射率振幅灵敏度可达到41.37%/RIU; 待测样品折射率一定时, 厚度频率灵敏度随其厚度的增大而线性减小; 随着待测样品厚度的增加, RFOM呈增大趋势, 但增大幅度在逐渐减小; TFOM随待测样品厚度的增加而减小.     

基于耦合开口方环共振空腔的可控法诺共振研究

基于表面等离子激元理论与金属-介质-金属波导结构提出一个由开口方环共振空腔、挡板及MIM波导组成的波导结构,并使用有限元方法系统地研究了该结构的透射特性.仿真计算结果表明:该结构可以产生法诺共振现象,其共振波长可以通过改变开口方环空腔的长度及开口大小进行调节,该结构敏感度可达1 600nm/RIU,品质因数为1.31×10~5.此外,通过调整方环共振空腔上开口的位置,在波导中产生了双重法诺共振现象,其敏感度可达1 700nm/RIU,品质因数为8.3×10~4.该结构有望在光学集成回路,尤其是纳米生物传感器方面得到比较广泛的应用.     

基于耦合T型空腔的多重法诺共振现象

提出由T型空腔和挡板组成的两种金属-电介质-金属(MIM)波导结构,分别为:正T型空腔结构和倒T型空腔结构,并应用有限元法系统地研究了该结构的透射特性.对于正T型空腔结构,仿真结果出现了双重法诺共振现象,并且共振波长可以通过改变T型空腔长度和高度进行调节.该结构有助于设计成敏感度达到1 620nm/RIU、品质因数为5.4×10~4的纳米传感器.对于倒置T型空腔,在波导中产生了多重法诺共振现象,其敏感度可达1 560nm/RIU,品质因数为9.37×104.该结构有望在光学集成回路,特别是纳米传感器、光束分路器方面具有广泛应用.     

基于全相位滤波技术的光纤表面等离子体共振传感解调算法

基于生物样品检测对折射率传感的迫切需求,构建一种全光纤表面等离子体共振(surface plasmon resonance,SPR)系统,并针对其设计了基于全相位滤波技术的SPR特征波长传感解调算法.基于系统仿真,理论计算了光纤SPR传感器的折射率传感灵敏度.采用全相位滤波技术提取光纤SPR传感器透射光谱的特征波长,理论推导了全相位滤波器的解析表达式.实验结果表明,使用本算法的光纤SPR传感器折射率传感灵敏度为1640.4 nm/RIU,折射率检测的分辨率是7.36×10~(-4)RIU,与传统方法相比,有效提高了系统的检测精度和抗光源扰动性能,降低了实验成本.