一种低损耗的对称双楔形太赫兹混合表面等离子体波导

本文研究了一种适用于太赫兹频段的对称双楔形混合等离子体波导.采用有限元法对其混合模式特征进行数值模拟,阐述了波导的传播长度、归一化有效模场面积和品质因子等特性随波导几何参数的变化规律.结果表明,对称双楔形混合等离子体波导在太赫兹频段可获得良好的模场约束能力和低损耗特性,在有效模场面积达到λ2/10280时,传播长度达到51 × 103 μm.波导参数最优时的平行对称楔形波导在忽略波导间串扰时,波导间距小于16 μm时的耦合长度约为8958 μm.通过对比发现,相比于先前的对称微楔形波导结构和对称蝴蝶结波导结构,对称双楔形混合等离子体波导在传输特性和耦合特性方面都具有更大的优势,将在光学力捕获、生物分子传输以及高密度集成电路设计等方面具有潜在的应用前景.     

纳米金属肋混合表面等离子体波导模式特性分析

基于传统混合表面等离子体波导,提出了一种半导体纳米线和纳米金属肋混合的表面等离子体波导.采用有限元法对其模式特性进行了数值模拟,研究了该波导的有效折射率、传播损耗、归一化模场面积等特性随波导几何尺寸的变化规律,分析了该混合波导的增益阈值.结果表明:该波导具有较低的传播损耗和较强的光场限制能力,并且混合模式的最小模面积仅为0.001 52μm2.     

共面蝴蝶结混合表面等离子体波导模式特征研究

基于传统纵向蝴蝶结混合表面等离子体波导(BTHPW),提出一种共水平面BTHPW集成光波导结构,是由半导体硅肋和金属Ag肋两种波导对放在一个SiO_2基底面上构成,采用有限元法对其混合模式特征进行数值模拟,分析该波导传播长度、归一化有效模场面积和品质因子等特性随波导几何尺寸的变化规律。结果表明,该波导模式具有传播损耗较小同时又较强光限制能力的特点,最长传播距离可达108μm,最小有效模面积可达λ~2/3000左右。该波导结构制作工艺简单,并可应用于高灵敏度折射率传感器和微纳米光子集成器件等领域。     

非线性介质的表面等离子体波导设计和优化

设计了一种基于非线性介质Si-NC/SiO2的混合表面等离子体波导,利用有限元方法定量分析了这种波导所支持基模的能流密度分布、有效折射率、传播长度和有效面积与几何结构参数以及非线性介质的依赖关系.分析结果表明,光场主要被限制在非线性区域,通过调节非线性层的厚度以及非线性比例因子,可以实现模式的有效折射率和传播长度等传输特性参数的调节.固定非线性介质比例因子,有效折射率和传播距离随非线性层厚度增加而增大;固定波导尺寸,有效折射率随比例因子增大而增大,传播距离和有效面积较小.最后,根据分析结果对非线性效应进行优化,优化后波导最优结构尺寸为波导宽度为250nm,非线性材料层厚度为100nm,硅层厚度为150nm.     

领结形中空表面等离子体波导的传输特性

设计了一种领结形中空表面等离子体波导.采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率、传播长度和模式面积随几何结构参数和工作波长的依赖关系进行了分析.结果表明,沿纵向的能流主要分布在两个上下突起所形成的中间区域.通过调整几何参数及工作波长,可以调节模式的有效折射率、传播长度和模式面积.在工作波长确定的条件下,有效折射率随突起半径的增大呈减小趋势,而传播长度和模式面积则随着突起半径的增大呈增大趋势,四个角上的圆弧半径对波导的传输特性有微调作用,左右扇形区域的半径对波导的传输特性有较明显 关键词： 集成光学 光波导 表面等离子体波导     

梯形截面硅基水平多槽纳米线定向耦合器全矢量分析

定向耦合器是构成各类光子器件的基础元件. 本文采用一种基于电场分量的全矢量有限元法, 分析由梯形截面硅基水平多槽纳米线构成的定向耦合器. 给出了准TE与准TM偶、奇模有效折射率、耦合长度及模场分布, 揭示了其模式的混合特性及模场分布特点. 分析结果表明, 准TE模与准TM模的耦合长度随波导间距的增大均呈指数增长, 其中准TE模的耦合长度对波导侧壁倾角的变化敏感, 而准TM模的耦合长度对槽厚及槽折射率的变化敏感. 恰当选择结构与材料参数, 可实现两偏振态下相同耦合长度, 定向耦合器在偏振无关条件下工作.     

紫外表面等离激元在基于氧化锌纳米线的半导体-绝缘介质-金属结构中的输运特性研究

研究了紫外表面等离激元在半导体纳米线-绝缘介质-金属构成的波导结构中的输运问题,借助有限元方法,对这种波导所支持导模的电磁能分布、有效折射率、传播长度和有效模场面积随电磁参数和几何结构参数的依赖关系进行了分析.计算结果表明:以氧化锌纳米线作为增益介质,绝缘材料选择折射率小的空气,金属选择铝能够实现对输出光场的亚波长约束,有效模场面积达到λ2/100,同时保持低的传输损耗和高场强限制能力;有望用作纳米光源,使得相关的生物探测器件和医疗诊断设备实现更高的灵敏度和更小的体积.     

蝴蝶形中空表面等离子体波导的传输特性

本文设计了一种蝴蝶形中空表面等离子体波导,并对其传输特性进行了研究.采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率、传播长度和模式面积随几何参数和工作波长的变化关系进行了分析.结果表明:沿纵向的能流主要分布在由四个圆洞所构成的上下两个尖角之间的区域,且越接近尖角,沿纵向的能流越大.对中空圆洞的半径、上下两排圆洞圆心间横向距离和左右两列圆洞圆心间的纵向距离进行调节,模式的有效折射率、传播长度和模式面积也随之变化.在工作波长确定的条件下,相对于b=r/4的情况来说,当b=r/2时,上下两个尖角之间的距离较大,场与金属的相互作用较弱,有效折射率就较大,传播长度也较大.在几何参数确定的条件下,相对于λ=705.0 nm的情形来说,在λ较大时,场的分布范围较大,场与金属表面的接触面积较大,场与金属的相互作用较弱,有效折射率较小,传播距离较长.与由两个和三个空心圆柱构成芯区的表面等离子体波导相比较,蝴蝶形中空表面等离子体波导具有良好的传输特性.如果在波导结构中心填充增益介质,可以克服较大的传播损耗,因此这种蝴蝶形中空表面等离子体波导可以用于光子器件集成领域和传感器领域.     

一种硅基金属狭缝表面等离子体波导的设计

设计了一种适用于光电子集成电路的表面等离子体波导结构.利用三维全矢量时域有限差分法对该波导结构进行了数值模拟,并分析了其在基模传输时的模式场分布与金属结构顶角的关系以及其能量限制性.研究了该波导结构在不同金属材料下的有效折射率和传播长度对芯层宽度的依赖关系,讨论了两个该波导结构之间的耦合长度、最大转移功率和彼此间的串扰.结果表明:光场被高度限制在芯层区域,在金属结构顶角为135°时,其能量限制因子更高;在金属材料确定的情况下,有效折射率随芯层宽度增大而减小,而传播长度增大;在芯层宽度一定的条件下,两个波导结构间的耦合长度随波导间距增大而增大,最大转移功率和串扰随波导间距增大而减小.     

双椭圆纳米金属棒构成的表面等离子体波导的传输特性分析

设计了一种双椭圆纳米金属棒表面等离子体波导,采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率和传播长度随几何结构参数和工作波长的依赖关系进行了分析.结果表明,沿纵向的能流主要分布在两个椭圆金属棒所形成的中间区域,且越靠近金属棒的弧形边,沿纵向的能流越大.通过调节两个金属棒的中心距离以及它们的两个半轴的大小,可以调节模式的有效折射率和传播长度.在工作波长确定的条件下,相对于a=b的情形来说,在a<b时,场与金属表面接触的面积较大,场 关键词： 集成光学 光波导 表面等离子体波导     

A long-range hybrid THz plasmonic waveguide with low attenuation loss

Numerical solutions are obtained for the proposed novel hybrid terahertz plasmonic waveguide structure, namely the silicon metal silicon (SMS) waveguide. It is shown that the SMS waveguide can overcome the diffraction limit while still maintaining a sizeable propagation length. The geometric dependence of the mode characteristics of this structure is analyzed in detail, showing strong confinement and low loss with propagation lengths exceeding 14 mm at normalized mode areas of 1.72 × 10⁻². By using the FEM method (Comsol), the guiding properties of the hybrid terahertz surface plasmon polariton (HTSPP) waveguide are numerically analyzed at the THz frequency, and a combination of double-structured comparisons of the best features of the terahertz plasmonic waveguide is made. Depending on the height used and how the mode confinement is measured, various modal designs, such as double microwire structures, are developed. The structures indicate that we verified the possibility of low attenuation loss of hybrid THz plasmonics propagation. The effective mode area A_eff, energy distribution, and propagation length L_p versus height for waveguides with Si microwire and SiO₂ are shown. The numerical calculation results reveal a potential for use in applications such as optical force in trapping and transporting biomolecules, and in high-density integrated circuits.     

Terahertz multi-metal-wire hybrid-cladding hollow waveguide for refractive index sensing

We propose a design of terahertz refractive index sensing based on the multi-metal-wire(MMW) hybrid-cladding hollow waveguide. The proposed terahertz hybrid-cladding hollow waveguide comprises one air core in the center surrounding MMW surrounded dielectric. The central air core is used for filling lossless measurands and transmitting terahertz light. In particular, the refractive index sensing is realized by measuring the mode field area(MFA) variation of radially polarized mode. The modal effective refractive index, mode field intensity distribution, and mode field area properties responding to the measurand refractive indexes for different operating frequencies and structure dimensions are investigated, respectively.Simulations show that the proposed terahertz refractive index sensor can realize easily the measurement of the measurand refractive index. Meanwhile, the effects of operating frequency and structure parameters on sensitivity and measurement accuracy are also studied. In view of the trade-off between sensitivity and measurement accuracy, the reasonable choice of the operating frequency and structure parameters can optimize appropriately the sensitivity and measurement accuracy, and the sensitivity can reach approximately 0.585 mm~2/RIU(RIU is short for refraction index units) with the proper frequency and structure parameter.     

内壁涂覆石墨烯的双椭圆中空表面等离子波导

本文设计了一种内壁涂覆单层石墨烯的双椭圆形中空表面等离子波导,采用有限元的方法对其传输特性进行了研究。结果表明,椭圆之间的距离和半短轴的长度增大时,有效折射率的实部减小,传输距离增大,模式面积减小;圆化半径增大时,有效折射率的实部增大,传输距离减小,模式面积增大;工作频率增大时,有效折射率的实部减小,传输距离减小,模式面积减小;温度升高时,有效折射率先增大后减小,传输距离减小,模式面积减小。本文的工作为研究基于石墨烯的波导器件提供了理论依据。     

Enhancing Bremsstrahlung production from ultraintense laser-solid interactions with front surface structures

A new type of a coaxial multi-layer plasmonic waveguide is proposed. The mode propagation properties are analyzed at the communication working wavelength. Theoretical investigations reveal that the enhanced optical confinement can be achieved in the two low-index dielectric media layers. The mode size can be sub- or deep sub-wavelength scale. The mode propagation loss can be well compensated by replacing the high-index dielectric media with gain material to achieve longer propagation length with better mode confinement. The comparisons of the mode properties between the proposed waveguide and waveguides studied in the published literatures are also considered. These investigations potentially lay the groundwork for the further applications of nanowire type multilayer hybrid structures. This structure could also enable various applications such asnanophotonic waveguides, high-quality nanolasers, and optical trapping and biosensors.     

Long-Range Slot Hybrid Surface Plasmon Waveguide With Long Propagation Distance and Tight Mode Confinement

A long-range hybrid slot surface plasmon waveguiding structure that is capable of achieving ultra-small mode confinement and a long propagation distance simultaneously is proposed in this article. In comparison with the conventional long-range hybrid surface plasmon waveguide, the proposed waveguide can provide one order smaller mode area and a longer propagation distance by introducing a through-slot in the gap region. Meanwhile, the practical fabrication errors have little influence over mode properties of the waveguide. These results indicate that our designed waveguide can be a potential candidate for high-performance nanophotonic circuit and device.     

A hybrid long-range surface plasmon waveguide comprising a narrow metal stripe surrounded by the low-index dielectric regions

A novel hybrid long-range surface plasmon waveguide structure comprising a narrow metal stripe, two relative low-index dielectric regions and dielectric ridges is proposed and analyzed. With the dielectric ridges and the two relative low-index dielectric regions symmetrically distributed on both sides of the narrow metal stripe, a symmetric hybrid long range mode with low electromagnetic transmission loss and subwavelength scale confinement is achieved. By optimizing the parameters, the propagation length of the proposed waveguide is increased to over two times to that of the conventional symmetric dielectric loaded surface plasmon waveguide, but the mode size only increases about 20%. For this benefit, the hybrid long-range surface plasmons waveguide is a good candidate for realizing high density photonic integration circuits.     

Low-loss metal-insulator-semiconductor waveguide with an air core for on-chip integration

In this paper, a novel metal-insulator-semiconductor waveguide with an air core in the insulator layer is proposed in order to improve the on-chip integration. Compared with the structure with homogeneous insulator, the introduced air core provides an additional degree of freedom for tuning the characteristics of the hybrid plasmonic mode. Simulation results demonstrate that the proposed structure exhibits better tradeoff between the mode confinement and the propagation length. The relatively low crosstalk between adjacent proposed waveguides could be achieved and the coupling efficiency between conventional silicon waveguide and the proposed structure maintain. The proposed waveguide could be used to build ultra-compact photonic components and enable on-chip integration of photonic circuits.     

金属包层对称平面单轴晶体波导的模式场(Ⅱ)

对于晶体光轴平行于波导界面的结构,讨论了光在金属包层对称平面单轴晶体波导(波导层是单轴晶体,两个波导界面均为金属)内的传输特性.解析地得到了这种结构下波导模式场的精确解.模式场的性质因单轴晶体的性质不同而异.对于正单轴晶体,波导的主模是横电波,任何频率的光波均可激励该模式;当频率满足一定条件时,波导内传输单模,否则,将激励起高阶模式.高阶模既非TE波,也非TM波,而是两者耦合而成的混合模.对于负单轴晶体,波导的主模是一种混合模,该模式同样可被任何频率的光波所激励;当频率满足一定条件时,波导内传输单模,否则 关键词： 平面金属波导 单轴晶体 模式场 混合模     

Propagation properties of a modified surface plasmonic waveguide with an arc slot

We introduce a modified surface plasmonic waveguide with an arc slot. The dependences of distribution of energy flux density, effective index, propagation length and mode area of the symmetric mode supported by this waveguide on geometrical parameters and working wavelength are analysed by using the finite-difference frequency-domain (FDFD) method. Results show that the energy flux density distributes mainly in four corners which are formed by two arcs, and the closer to the corners it is, the stronger the energy flux density will be. The effective index, the propagation length and the mode area are influenced by geometrical parameters, including the width, the thickness and the arc radius of the surface plasmonic waveguide, as well as the working wavelength. It has been shown that the surface plasmonic waveguide with an arc slot has better propagation properties than the surface plasmonic waveguide with a straight slot. This work may be helpful for applying the slot surface plasmonic waveguide to integrated photonics.     

基于耦合介质纳米线的深亚波长局域波导

提出了一种基于耦合介质纳米线的深亚波长局域波导,通过两根紧邻的高折射率介质纳米线的耦合,该波导可以将光场有效束缚在纳米线之间的低折射率纳米缝隙中. 计算模拟的结果表明,该波导的有效模场面积达到Λ²₀/200,比单根纳米线波导小一个数量级,这种深亚波长的模场束缚能力可以与表面等离激元混合波导相比拟. 计算模拟的结果还表明,纳米线可能带有的低折射率氧化膜、低折射率衬底的存在、以及纳米线间尺寸存在的一定差异对于该波导结构的实际应用都不会产生很大 关键词： 介质波导 亚波长局域 表面等离激元波导 纳米线