基于石墨烯等离激元及六方氮化硼的微纳光器件的研究

发布时间：2018-06-07 12:34

  本文选题：石墨烯等离激元 + 双曲超材料　； 参考：《北京交通大学》2017年博士论文

【摘要】：在过去的十多年中,石墨烯这种内部碳原子呈蜂窝状排布的二维材料的足迹遍布从柔性电子器件到电子墨水等一系列的应用之中。石墨烯的存在不仅为我们显著提升现有微纳器件性能指出了新的方向,更使得设计具有新型功能的石墨烯器件成为了可能。与传统等离激元相比,石墨烯等离激元具有许多卓越的性质,例如可调谐的载流子浓度以及更强的场束缚能力。六方氮化硼是一种具有双曲色散曲线的天然范德华晶体,并且其内部支持的双曲声子极化模式具有与石墨烯等离激元相接近的色散特性,但更低的传输损耗。石墨烯-六方氮化硼异质结具有众多优越特性,例如作为衬底,能够维持覆盖在其表面石墨烯的杰出电学特性以及支持等离激元-声子极化混合模式的传播等等。等离激元-声子极化混合模式因兼具有石墨烯等离激元的宽带性,可调谐性以及双曲声子极化模式的低损耗特性而成为了新兴的研究热点。本文的主要研究成果以及创新点简述如下:1.首次提出了基于石墨烯-介质多层结构的双曲超材料波导并分别通过数值计算以及等效介质理论研究了其内部所支持模式的传播特性。超材料本身所具有的双曲色散特征允许该波导支持具有高达90的有效折射率的模式的传播。在由两个相同的双曲超材料波导并列放置而形成的缝隙波导结构中,缝隙区域中电场的幅值可以被增强约20倍且有高于70%的模式能量被束缚在其中,这大大优于之前报道的基于硅以及传统双曲超材料的缝隙波导结构。2.首次利用在磁光晶体上石墨烯等离激元传播的非互易性设计了一系列基于石墨烯等离激元的非互易器件,包括等离激元环形器,等离激元隔离器,磁控等离激元逻辑门器件和非互易等离激元振子。其中石墨烯等离激元隔离器能够实现低至2 dB的插入损耗以及高达42 dB的消光比,并且其使能方向可以通过外加磁场的方向进行控制。根据逻辑布尔运算(Boolean Algebra)设计了磁控石墨烯等离激元逻辑门器件。逻辑门器件对于沿某一方向输入的等离激元逻辑表达为或门(OR)或与门(AND),而对相反方向输入的等离激元表达为与非门(NAND)或或非门(NOR)。其中或门和与非门具有3 dB的插入损耗并能够实现高达13.6 dB的消光比,而与门和或非门具有2.5 dB的插入损耗以及最低为17.5 dB的消光比。非互易等离激元振子基于石墨烯覆盖的磁光材料纳米线结构,当上述结构与一个普通石墨烯片状波导相耦合时,两者组成具有非互易透射率的石墨烯等离激元滤波器,同样也具有实现等离激元隔离器的潜力。隔离器的消光比可以通过外加磁场的大小来进行调节并且其使能方向可以通过反转外加磁场的方向来进行切换,在适当的外加磁场以及结构参数下该隔离器可以实现大于25 dB的消光比。3.首次提出了基于石墨烯覆盖的锥形介质纳米线的探针结构,用于在红外波段实现强场增强效应。绝热近似模型以及数值计算结果显示石墨烯覆盖的锥形纳米线探针能够实现比普通锥形金属探针强约一个数量级的场增强效应且最大场幅值增强因子为24。提出了石墨烯覆盖的纳米线波导对结构,并分别分析了波导对结构所支持的六个最低阶模式的有效折射率,归一化传播长度,表面电荷分布以及模场分布情况。根据研究结果,六个最低阶的模式可以根据其杂化情况分为单极子-单极子杂化类型以及双极子-双极子杂化类型。研究发现在纳米线波导对缝隙区域的场增强因子可以高达107,相较于银纳米线波导对而言至少提升了六个数量级。除此之外,两个纳米线之间的梯度力高达20 nN/μm×mW,高于银纳米线波导对以及其他之前提出的缝隙波导结构50倍有余。4.首次提出了基于石墨烯覆盖的螺旋形介质光栅或石墨烯上覆盖的螺旋型三角金属天线阵列的圆偏振分析仪。当介质光栅或三角金属天线作为激发源且激发源阵列的几何相位效应与入射圆偏振光所携带的自旋角动量相同或相反时,在透镜中心等离激元被分别聚焦为空心圈状或实心点状分布。得益于石墨烯等离激元的可调谐性,在不影响分析仪工作特性的前提下,分析仪的工作波长可以通过石墨烯费米能级来加以调节,并能够实现高达550的消光比。首次采用具有排列为螺旋型且指向方向互相垂直的两列矩形纳米金属天线实现等离激元定向激发的方式来提升圆偏振分析仪的性能。在等离激元定向激发的作用下,圆偏振分析仪所实现的消光比将会被进一步提升至103以上。5.首次提出六方氮化硼缝隙波导结构并研究其缝隙区域支持的场增强效应,模式能量束缚效应以及两个六方氮化硼波导之间的梯度力现象。二维结构的六方氮化硼缝隙波导可以实现接近于60的场增强因子,接近于80%的功率束缚因子以及-8.5 nN/μm×mW的梯度力,这大大高于基于传统双曲超材料的缝隙波导结构。长1 μm的三维缝隙波导结构可以实现约为-1.2 nN/mW的梯度力以及约为50%的功率束缚因子。利用数值计算分析了在楔形石墨烯-六方氮化硼异质结中存在的纳米聚焦效应。异质结中存在的等离激元-声子极化混合模式具有相对于双曲声子极化模式更小的模式损耗以及依赖于六方氮化硼平板波导厚度的色散特性。和楔形六方氮化硼波导相比,楔形异质结能够实现高于60的归一化场幅值的增强因子。
[Abstract]:In the past more than 10 years, the footprint of graphene as a honeycomb like two-dimensional material has been found in a series of applications, ranging from flexible electronic devices to electronic ink. The existence of graphene has not only pointed out new directions for improving the performance of existing micro devices, but also made the design of a new functional stone. Graphene devices have become possible. Compared with the traditional plasmons, graphene and other excitations have many excellent properties, such as tunable carrier concentration and stronger field binding ability. Six square boron nitride is a natural Fan Dehua crystal with hyperbolic dispersion curve, and its internal supported hyperbolic phonon polarization mode has the same type. Graphene, such as the dispersion characteristics near the excimer, but lower transmission loss. The graphene six square nitride boron heterojunction has many superior properties, for example, as a substrate, it can maintain outstanding electrical properties covering the surface of graphene on its surface and the propagation of the polaron polarization mixing mode and so on. The hybrid mode has become a new research hotspot because of the wideband, tunability and low loss characteristics of the hyperbolic phonon polarization mode, such as graphene. The main research results and innovation points of this paper are as follows: 1. the hyperbolic supermaterial waveguide based on graphene medium multi layer structure was first proposed and passed respectively. The numerical calculation and the equivalent medium theory study the propagation characteristics of the mode supported within it. The hyperbolic dispersion characteristics of the supermaterial itself allow the waveguide to support the propagation of the mode with up to 90 effective refractive index. In the slot waveguide structure formed by the parallel placement of two same hyperbolic hypermaterial waveguides, the gap Zone The amplitude of the electric field in the domain can be enhanced by about 20 times and the mode energy is higher than 70%, which is greatly superior to the previously reported slotted waveguide structure based on silicon and traditional hyperbolic hypermaterials (.2.), for the first time, a series of excitations based on graphene, such as graphene, were designed for the nonreciprocity of the plasmons, such as magneto and Light crystals. The non reciprocal devices of the element include the equal ionization polaritator, the plasmons isolator, the magnetron and other excitter logic gate devices and the non reciprocal excitations. In which the graphene isolator can achieve the insertion loss as low as 2 dB and the extinction ratio up to 42 dB, and its direction can be carried out in the direction of the applied magnetic field. Control. Based on logical Boolean operation (Boolean Algebra), a logic gate device, such as magnetically controlled graphene, is designed. The logic gate device is expressed as a gate (OR) or a gate (AND), which is input in a certain direction, and a NAND or or non gate (NOR), which is input to the opposite direction, is a or a non gate and a non gate (NOR). The gate has an insertion loss of 3 dB and can achieve a extinction ratio of up to 13.6 dB, while the insertion loss of the gate and or non gate has 2.5 dB and the lowest extinction ratio of 17.5 dB. The non reciprocal plasmon oscillator based on the graphene covered magneto optic nanowire structure, when the above structure is coupled with an ordinary graphene sheet waveguide, two They also have the non reciprocal transmittance graphene filter, which also has the potential to realize the isolator. The extinction ratio of the isolator can be adjusted by the size of the applied magnetic field and the direction of the energy can be switched by reversing the direction of the applied magnetic field, in the proper external magnetic field and the junction. Under the structure parameter, the isolator can achieve the extinction ratio of more than 25 dB..3. first proposed a probe structure of the tapered dielectric nanowires based on graphene, which can be used to achieve strong field enhancement in the infrared band. The adiabatic approximation model and numerical results show that the cone nanowire probe covered with graphene can be compared to the common cone. The field enhancement effect of a metal probe is approximately one order of magnitude and the maximum field amplitude enhancement factor is 24.. The structure of the nanowire waveguide covered by Shi Moxi is proposed. The effective refractive index, the normalized propagation length, the surface charge distribution and the mode field distribution of the six lowest order modes supported by the waveguide structure are analyzed. As a result, the six lowest order modes can be divided into monopole monopole hybrid and bipolar subbipolar hybrids according to their hybrids. It is found that the field enhancement factor of the nanowire waveguide can be as high as 107, and at least six orders of magnitude higher than that of the silver nanowire waveguide pair. Two The gradient force between the nanowires is up to 20 nN/ mu m x mW, which is higher than the silver nanowire waveguide pair and the other proposed slot waveguide structure 50 times more than that of the circular polarization analyzer based on the spiral dielectric grating or the spiral triangular metal antenna array covered by graphene. When the metal antenna is the excitation source and the geometric phase effect of the excitation source array is the same or the opposite of the spin angular momentum carried by the incident circular polarized light, the exciter in the center of the lens is focused on the hollow circle or the solid point distribution respectively. The working wavelength of the analyzer can be adjusted by the Fermi level of graphene, and the extinction ratio up to 550 can be achieved. For the first time, the performance of a square to improve the circular polarization analyzer with a two column rectangular nanoscale antenna arranged in a spiral and pointing direction to each other is realized. Under the action of polaritons directional excitation, the extinction ratio of the circular polarization analyzer will be further enhanced to more than 103.5.. The first proposed six square boron nitride slot waveguide structure and the field enhancement effect, the mode energy binding effect and the gradient force between the two six square boron nitride waveguides. The six square boron nitride slot waveguide can achieve a field enhancement factor of close to 60, close to 80% of the power bound factor and the gradient force of -8.5 nN/ m x mW, which is greatly higher than the gap waveguide structure based on the traditional hyperbolic hypermaterials. The three-dimensional slot waveguide structure with a long 1 u m can achieve a gradient force of about -1.2 nN/mW and about 50% of the work. The rate bound factor is used to analyze the nanoscale focusing effect in the wedge graphene six square nitride heterojunction. The isoplasmon phonon polarization mixed mode in the heterojunction has smaller mode loss compared with the hyperbolic phonon polarization mode and the dispersion dependence on the thickness of the six square boron nitride plate waveguide. Compared with wedge-shaped six boron nitride waveguides, wedge-shaped heterojunction can achieve an enhancement factor higher than 60 of normalized field amplitude.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN256
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本文编号：1991189