High-sensitivity refractive index sensors based on Fano resonance in a metal-insulator-metal based arc-shaped resonator coupled with a rectangular stub

A metal-insulator-metal(MIM)-based arc-shaped resonator coupled with a rectangular stub(MARS) structure is proposed. This structure can generate two tunable Fano resonances originating from two different mechanisms. The structure has the advantage of being sensitive to the refractive index, and this feature makes it favorable for application in various microsensors. The relationship between the structural parameters and Fano resonance is researched using the finite element method(FEM) based on the software COMSOL Multiphysics 5.4. The simulation reveals that the sensitivity reaches1900 nm/refractive index unit(RIU), and the figure of merit(FOM) is 23.75.

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.

基于NL-PF和MIMS的CT金属伪影消除算法

建立了一套针对由金属伪影造成的CT图像质量退化的恢复算法。利用Non-Local前置滤波(Non-Local Pre-filter,NL-PF)对原始CT图像进行全局滤波,从而有效地滤除原始图像中的噪声并对射线状金属伪影进行了平滑,其后配合最大互信息量分割算法(Mutual Information Maximized Segmentation,MIMS)从图像中分割出伪影成份,并利用其周围非伪影部分的像素对伪影类像素进行插值处理得到一个称之为"伪组织"类的图像。最后,通过融合"伪组织"图像的sinogram和原始CT图像的sinogram,得到校正的sinogram并采用滤波反投影重建算法完成金属伪影的CT校正图像。利用所提出的方法可以对含有金属伪影的CT图像进行有效伪影消除,其中射线状伪影消除效果显著。另外,此方法还可以锐化器官轮廓,避免了临床上由于金属伪影导致的放射治疗效果下降。实验表明,金属伪影消除算法可以有效地消除高密度物体造成的金属伪影,从而提高临床诊断和治疗的效果提供技术支持。

基于MIM波导缺陷谐振环结构的传输特性研究

应用时域有限差分方法(FDTD)研究了基于金属-介质-金属(MIM)波导缺陷谐振环结构的传输特性.该结构由一通道波导和位于通道上方的缺陷谐振环组成,与无缺陷谐振腔结构相比,缺陷谐振环结构破坏了环形腔原有的共振模式,从而呈现出新颖的滤波特性.当缺陷尺寸发生改变时,谐振环有效长度发生变化,通过调整缺陷的尺寸,可以有效调节滤波波长,其数值计算值与传输线理论值基本吻合.此外,通道波导与谐振环间的耦合强度在一定程度上依赖于缺陷的位置,因此通过调节缺陷的位置可以有效控制滤波强度.与其他滤波器相比,此结构在不改变结构总尺寸的情况下,可调节滤波波长,实现了更宽频段的滤波,并有效调节其透射率.当缺陷尺寸设定为某一特定值时,能实现模式间的简并,提高滤波性能.

基于SPPs的方形凹环结构MIM滤波器设计

基于表面等离子体波的传播特性提出了一种由方形凹环与波导管耦合而成的MIM结构滤波器,运用有限元法数值计算获得了该滤波结构的磁场分布、透射谱和共振波长分布曲线.研究结果表明,其阻带透射率最小透射比可低至0.01,通带最大透射比则高达0.96,并且顶部分布平滑.在增大滤波器波导结构参数I、H时,相应的透射谱线会有明显的红移,且不同模式阻带的透射比也会随之改变,此外共振波长与结构参数的变化呈现线性关系.在增大结构参数D时,模式1的透射率从之前的0.63增加到0.80,模式1最终消失,其余模式几乎不变,同时共振波长分布与参数D的变化无关.通过结构参数的优化,可以使波导结构的品质因数从14.82提升到17.07,通频带亦有所增加.该MIM结构滤波器具有封装尺寸小、多模式、阻带较窄、通带平滑、良好的品质因数以及可调节性,在微纳集成光学器件尤其是波分复用系统中有着良好的应用前景.

A Novel Adjustable Plasmonic Filter Realization by Split Mode Ring Resonators

A novel nanoscale plasmonic filter consisting of two coupled metal-insulator-metal (MIM) waveguides is introduced. The new structure functionality is verified by numerical simulations in different configurations of the filter. The impedance variation characteristic named as split mode ring resonancy is achieved by partially narrowing or expanding the waveguide diameter. The main parameters of the filter are evaluated by using the parameters of an implemented type of ring resonator. Moreover, modal analysis for Surface Plasmon Polariton (SPP) propagation is performed while changing the main spatial parameters of the device.

Simulation and Design of a Submicron Ultrafast Plasmonic Switch Based on Nonlinear Doped Silicon MIM Waveguide

We propose and analyze a submicron stub-assisted ultrafast all-optical plasmonic switch based on nonlinear MIM waveguide. It is constructed by two silicon stub filters sandwiched by silver cladding. The signal wavelength is assumed to be 1550 nm. The simulation results show a ?14.66 dB extinction ratio. Downscaling the silicon waveguide in MIM structure leads to enhancement of the effective Kerr nonlinearity due to tight mode confinement. Also, using O+ ions implanted into silicon, the switching time less than 10 ps and a delay time less than 8 fs are achieved. The overall length of the switch is 550 nm.

MIM电容器及其在慢波滤波器设计中的应用

为提升微波电路的集成度,提出了一种基于印刷电路板(PCB)的金属-绝缘体-金属(MIM)电容器,并将其应用在小型化慢波带通滤波器(BPF)设计中。该MIM电容器由一对刻蚀在基板两侧的正方形贴片组成,容值为5.26 pF,远大于传统的交指电容器的容值。进一步将该MIM电容器嵌入到一个传统的开环谐振器(OLR)内部空间中,形成一个慢波OLR。利用该慢波OLR设计了一种小型化二阶慢波BPF。与加载交指电容器的BPF相比,所提出BPF的尺寸缩减了40%。其阻带插入损耗在大于20 dB的频率范围达到其通带中心频率的4.46倍,表明所提出的BPF具有宽阻带特性。实测和仿真结果吻合较好。

Plasma-etching on monolithic MOFs-based MIM filter boosted chemical sensing

Metal-insulator-metal(MIM)cavity as a lithography-free structure to control light transmission and reflection has great potential in the field of optical sensing.However,the dense top metal layer of the MIM prohibits any external medium from entering the dielectric insulation layer,which limits the application of the cavity in the sensing field.Herein,we demonstrate a series of monolithic metal-organic frameworks(MOFs)based MIM cavities,which are treated by plasma etching to provide channels for chemical diffusion and to advance sensing.We modulate the bandwidth of the MIM filters by controlling the MOF thickness as insulator layers.Oxygen plasma-etching is applied to build channels on the top metal layer without altering their saturation and brightness for chemical sensing performance.The etching time regulates the number and size of channels on the top metal layer.Sensing behavior is demonstrated on the plasma-etched MOFs-based MIM cavity when external chemicals diffuse in the cavity.In addition,we generate patterned structure of the MOFs-based MIM cavity via plasma-mask method,which can transfer to different substrates and produce a controllable structure color change for chemical sensing.Our MIM cavity may promote the advancement and applications of structural color in security imaging,color display,information anticounterfeiting,and color printing.

一种新型小型化低成本高通滤波器

介绍了一种具有小型化、低成本特点的新型半集总参数高通滤波器。该滤波器在传统电感-电容(Inductance-Capacitance, LC)集总参数高通滤波器电路原型的基础上引入电感互耦,在阻带近端产生传输零点,提高了阻带近端的带外抑制。通过采用垂直安装的双层微波印制金属-绝缘体-金属(Metal Insulator Metal, MIM)电容,实现了半集总参数高通滤波器的小型化和高性能。同时,电路兼具加工工艺简单、成本低的优点。所提出的电路满足当前微波产品对电路小型化、高性能和低成本的需求。

基于CRLH TL结构的带通滤波器设计与研究

基于复合左右手传输线（CRLH TL）原理,利用微带与共面波导组合的双层介质结构,设计了一种新型带通滤波器.其等效左手电容由金属-绝缘体-金属（MIM）耦合结构提供,等效左手电感由蘑菇型零阶谐振器（MZOR）中的短路通孔实现.通过研究MZOR中U型槽长度变化对滤波器性能的影响得知,该带通滤波器具有结构紧凑,带宽较大,插入损耗较小等优点.HFSS仿真结果显示,滤波器的通带为3.4～7.2 GHz,通带内插入损耗低于-0.5 dB,回波损耗小于-11.5 dB.因此,该滤波器可应用于超宽带无线通信系统.

基于自适应方向性滤波和非局部均值修补的CT图像金属伪影消除

CT图像金属伪影的校正长期以来都是一个重要课题。首先采用自适应方向性前置滤波器对含有金属伪影的图像进行处理,在一定程度上消除噪声,抑制条状伪影;其后采用均值漂移分割出原图像中的金属成分,最大互信息熵分割出伪影成分;使用平行束投影获取原始图像和金属成分的弦空间数据,从原图弦空间数据中减除伪影成分对应的弦图;继而采用非局部均值修补结合线性插值方法对弦空间数据进行补全;最后采样滤波反投影得到校正后的图像。实验表明,本算法对于含有金属伪影的水模和真实临床图像的校正,获得更好的匀质区域一致性和更好的伪影抑制性能。

基于表面等离子激元的凸环结构金属-介质-金属滤波器设计

利用边界耦合的方法构造了金属-介质-金属结构滤波器,该结构由一个凸环谐振腔与一个波导管耦合而成.通过有限元法数值仿真得到了该凸环腔体波导结构的磁场分布图、透射谱线和谐振波长分布,分析了各结构参量对滤波器传输特性的影响.结果表明,所提出的凸环滤波器具有透射峰窄,谱线平滑等特点,且阻带透射率最低可达0.001,通带透射率最高可达0.977.增大结构参量h2和neff时,相应的透射谱会发生明显的红移,增大结构参量L1时,透射谱几乎无变化.对结构参量进行调整和优化,相应的谐振波长可分布在第一通信窗口(850nm)和第三通信窗口(1 550nm)附近,能够很好地运用于光通信中.

基于IPD工艺的高通滤波器芯片设计

设计采用了集成无源器件(Integrated Passive Device,IPD)工艺设计了一款集总式紧凑型椭圆函数高通滤波器。设计采用砷化镓GaAs作为衬底材料,基于寄生参数和等效电路模型对螺旋电感和MIM(金属-介质-金属)电容进行理论分析,并在三维电磁场仿真软件HFSS中进行建模与仿真。经过调试,该模型截止频率9.2 GHz,在9.8 GHz通带上插入损耗小于2 dB,在0~7.2 GHz阻带抑制>30 dB,尺寸仅为640μm×865μm×84μm,有效缩小了无源滤波器的尺寸,验证了基于GaAs IPD工艺的集总式高通滤波器设计的可行性。

基于Ba_xSr_(1-x)TiO_3薄膜电容的L波段可调滤波器

在蓝宝石基片上使用Ba_xSr_(1-x)TiO_3(BST)铁电薄膜电容作为可调元件制作出一种五阶梳状线可调带通滤波器。通过对BST平行板电容的材料特性(介电常数、损耗和可调率)的提取,其中40 V偏压下的可调率为43.1%,将这些特性运用于可调滤波器的制作。初步的实验结果分析表明,在20V直流偏置电压作用下,滤波器的中心频率从1.19GHz变化到1.31GHz(可调率为10.1%),带内插入损耗为13.5~13.7dB,回波损耗低于12dB。

Formation mechanism and modulation of electromagnetically induced transparency-like transmission in side-coupled structures

Based on Fabry model and finite-different time-domain(FDTD) method, the plasmonic structure composed of a metal-insulator-metal(MIM) bus waveguide and a side-coupled resonator was investigated. It is found that the transmission features can be regulated by the cavity width and coupling distance. Electromagnetically induced transparency(EIT)-like transmission can be excited by adding an identical resonator on the pre-existing structure. Combining the foregoing theoretical analysis with coupled mode theory(CMT), the formation process of the EIT-like transmission was detailedly analyzed. EIT-like transmission can also be excited in plasmonic structure with two detuned resonators. By altering the structure parameters, the transparency window can be purposefully modulated. With the merits of compact structure and simplicity in fabrication, the proposed structures may have a broad prospect of applications in highly integrated optical circuits.

Numerical analysis of end-fire coupling of surface plasmon polaritons in a metal-insulator-metal waveguide using a simple photoplastic connector

We propose a design for efficient end-fire coupling of surface plasmon polaritons in a metal-insulator-metal(MIM) waveguide with an optical fiber as part of a simple photoplastic connector. The design was analyzed and optimized using the three-dimensional finite-difference time-domain method. The calculated excitation efficiency coefficient of the waveguide is 83.7%(-0.77 dB) at a wavelength of 405 nm. This design enables simple connection of an optical fiber to a MIM waveguide and highly efficient local excitation of the waveguide.Moreover, the length of the metallic elements of the waveguide, and thus the dissipative losses, can be reduced.The proposed design may be useful in plasmonic-type waveguide applications such as near-field investigation of live cells and other objects with super-resolution.

Design and optimization of a nano-antenna hybrid structure for solar energy harvesting application

A novel hybrid structure with high responsivity and efficiency is proposed based on an L-shaped frame nano-antenna(LSFNA)array for solar energy harvesting application.So,two types of LSFNAs are designed and optimized to enhance the harvesting characteristics of traditional simple electric dipole nano-antenna(SEDNA).The LSFNA geometrical dimensions are optimized to have the best values for the required input impedance at three resonance wavelengths ofλ_(res)=10μm,15μm,and 20μm.Then the LSFNAs with three different sizes are modeled like a planar spiral-shaped array(PSSA).Also,a fractal bowtie nano-antenna is connected with the PSSA in the array gap.This proposed hybrid structure consists of two main elements:(I)Three different sizes of the LSFNAs with two different material types are designed based on the thin-film metal-insulator-metal diodes that are a proper method for infrared energy harvesting.(Ⅱ)The PSSA gap is designed based on the electron field emission proposed by the Fowler-Nordheim theory for the array rectification.Finally,the proposed device is analyzed.The results show that the PSSA not only has an averaged 3-time enhancement in the harvesting characteristics(such as return loss,harvesting efficiency,etc.)than the previously proposed structures but also is a multi-resonance wide-band device.Furthermore,the proposed antenna takes up less space in the electronic circuit and has an easy implementation process.

Analysis, design and simulation of MIM plasmonic filters with different geometries for technical parameters improvement

In this paper, four optical filter topologies based on metal–insulator–metal waveguides are proposed and the designed structures are investigated numerically using finite-difference timedomain method. Triangular-shaped adjunctions have been added to the filter structures to improve their transmission spectrum. These improved structures consist of air as the insulator and silver as the metal. The relative permittivity of metal has been described via the Drude,Drude–Lorentz, and Palik models. The first filter’s transmission spectrum shows an acceptable transmittance. In the second optimized filter, the transmission spectrum has been improved. The transmittance spectrum can be tuned through adjusting the edge of the triangle in these four optimized filters. As a result, the bandwidths of resonance spectra can be adjusted. The theory of such tapered structures will be investigated by the tapered transmission line and will be solved with the transfer matrix method. This method shows a better performance and higher transmission efficiency in comparison with the basic structures. On the other hand, the final filter has been chosen as the best one because of its hexagonal resonator. The main reason for having a better result is due to a longer interaction length in comparison with the circular resonator. This in turn creates much better energy coupling and results in higher transmission.

基于表面等离子激元的拱型谐振腔滤波器设计

基于边界耦合的方法构造一种基于金属-介质-金属(MIM)纳米谐振腔波导组成的滤波器,该结构由1个拱型谐振腔和1个矩阵波导管组成。通过有限元法(FEM)仿真分析拱型腔波导MIM结构滤波器的传输特性曲线、谐振波长和磁场分布图。研究结果表明该拱型腔滤波器具有平滑的传输曲线、平坦的通带、较宽的带宽,且通带透射率高达0.976,阻带透射率低至0.001,这表示此结构滤波器具有良好的滤波特性。通过对该拱型结构滤波器进行参数优化,可以在光通信波段的三个通信窗口上实现通道选择的滤波功能,该结构滤波器在高密度光集成电路和纳米光学中具有广阔的应用前景。