發(fā)布時(shí)間：2018-06-07 12:34

  本文選題：石墨烯等離激元 + 雙曲超材料　； 參考：《北京交通大學(xué)》2017年博士論文

【摘要】：在過(guò)去的十多年中,石墨烯這種內(nèi)部碳原子呈蜂窩狀排布的二維材料的足跡遍布從柔性電子器件到電子墨水等一系列的應(yīng)用之中。石墨烯的存在不僅為我們顯著提升現(xiàn)有微納器件性能指出了新的方向,更使得設(shè)計(jì)具有新型功能的石墨烯器件成為了可能。與傳統(tǒng)等離激元相比,石墨烯等離激元具有許多卓越的性質(zhì),例如可調(diào)諧的載流子濃度以及更強(qiáng)的場(chǎng)束縛能力。六方氮化硼是一種具有雙曲色散曲線(xiàn)的天然范德華晶體,并且其內(nèi)部支持的雙曲聲子極化模式具有與石墨烯等離激元相接近的色散特性,但更低的傳輸損耗。石墨烯-六方氮化硼異質(zhì)結(jié)具有眾多優(yōu)越特性,例如作為襯底,能夠維持覆蓋在其表面石墨烯的杰出電學(xué)特性以及支持等離激元-聲子極化混合模式的傳播等等。等離激元-聲子極化混合模式因兼具有石墨烯等離激元的寬帶性,可調(diào)諧性以及雙曲聲子極化模式的低損耗特性而成為了新興的研究熱點(diǎn)。本文的主要研究成果以及創(chuàng)新點(diǎn)簡(jiǎn)述如下:1.首次提出了基于石墨烯-介質(zhì)多層結(jié)構(gòu)的雙曲超材料波導(dǎo)并分別通過(guò)數(shù)值計(jì)算以及等效介質(zhì)理論研究了其內(nèi)部所支持模式的傳播特性。超材料本身所具有的雙曲色散特征允許該波導(dǎo)支持具有高達(dá)90的有效折射率的模式的傳播。在由兩個(gè)相同的雙曲超材料波導(dǎo)并列放置而形成的縫隙波導(dǎo)結(jié)構(gòu)中,縫隙區(qū)域中電場(chǎng)的幅值可以被增強(qiáng)約20倍且有高于70%的模式能量被束縛在其中,這大大優(yōu)于之前報(bào)道的基于硅以及傳統(tǒng)雙曲超材料的縫隙波導(dǎo)結(jié)構(gòu)。2.首次利用在磁光晶體上石墨烯等離激元傳播的非互易性設(shè)計(jì)了一系列基于石墨烯等離激元的非互易器件,包括等離激元環(huán)形器,等離激元隔離器,磁控等離激元邏輯門(mén)器件和非互易等離激元振子。其中石墨烯等離激元隔離器能夠?qū)崿F(xiàn)低至2 dB的插入損耗以及高達(dá)42 dB的消光比,并且其使能方向可以通過(guò)外加磁場(chǎng)的方向進(jìn)行控制。根據(jù)邏輯布爾運(yùn)算(Boolean Algebra)設(shè)計(jì)了磁控石墨烯等離激元邏輯門(mén)器件。邏輯門(mén)器件對(duì)于沿某一方向輸入的等離激元邏輯表達(dá)為或門(mén)(OR)或與門(mén)(AND),而對(duì)相反方向輸入的等離激元表達(dá)為與非門(mén)(NAND)或或非門(mén)(NOR)。其中或門(mén)和與非門(mén)具有3 dB的插入損耗并能夠?qū)崿F(xiàn)高達(dá)13.6 dB的消光比,而與門(mén)和或非門(mén)具有2.5 dB的插入損耗以及最低為17.5 dB的消光比。非互易等離激元振子基于石墨烯覆蓋的磁光材料納米線(xiàn)結(jié)構(gòu),當(dāng)上述結(jié)構(gòu)與一個(gè)普通石墨烯片狀波導(dǎo)相耦合時(shí),兩者組成具有非互易透射率的石墨烯等離激元濾波器,同樣也具有實(shí)現(xiàn)等離激元隔離器的潛力。隔離器的消光比可以通過(guò)外加磁場(chǎng)的大小來(lái)進(jìn)行調(diào)節(jié)并且其使能方向可以通過(guò)反轉(zhuǎn)外加磁場(chǎng)的方向來(lái)進(jìn)行切換,在適當(dāng)?shù)耐饧哟艌?chǎng)以及結(jié)構(gòu)參數(shù)下該隔離器可以實(shí)現(xiàn)大于25 dB的消光比。3.首次提出了基于石墨烯覆蓋的錐形介質(zhì)納米線(xiàn)的探針結(jié)構(gòu),用于在紅外波段實(shí)現(xiàn)強(qiáng)場(chǎng)增強(qiáng)效應(yīng)。絕熱近似模型以及數(shù)值計(jì)算結(jié)果顯示石墨烯覆蓋的錐形納米線(xiàn)探針能夠?qū)崿F(xiàn)比普通錐形金屬探針強(qiáng)約一個(gè)數(shù)量級(jí)的場(chǎng)增強(qiáng)效應(yīng)且最大場(chǎng)幅值增強(qiáng)因子為24。提出了石墨烯覆蓋的納米線(xiàn)波導(dǎo)對(duì)結(jié)構(gòu),并分別分析了波導(dǎo)對(duì)結(jié)構(gòu)所支持的六個(gè)最低階模式的有效折射率,歸一化傳播長(zhǎng)度,表面電荷分布以及模場(chǎng)分布情況。根據(jù)研究結(jié)果,六個(gè)最低階的模式可以根據(jù)其雜化情況分為單極子-單極子雜化類(lèi)型以及雙極子-雙極子雜化類(lèi)型。研究發(fā)現(xiàn)在納米線(xiàn)波導(dǎo)對(duì)縫隙區(qū)域的場(chǎng)增強(qiáng)因子可以高達(dá)107,相較于銀納米線(xiàn)波導(dǎo)對(duì)而言至少提升了六個(gè)數(shù)量級(jí)。除此之外,兩個(gè)納米線(xiàn)之間的梯度力高達(dá)20 nN/μm×mW,高于銀納米線(xiàn)波導(dǎo)對(duì)以及其他之前提出的縫隙波導(dǎo)結(jié)構(gòu)50倍有余。4.首次提出了基于石墨烯覆蓋的螺旋形介質(zhì)光柵或石墨烯上覆蓋的螺旋型三角金屬天線(xiàn)陣列的圓偏振分析儀。當(dāng)介質(zhì)光柵或三角金屬天線(xiàn)作為激發(fā)源且激發(fā)源陣列的幾何相位效應(yīng)與入射圓偏振光所攜帶的自旋角動(dòng)量相同或相反時(shí),在透鏡中心等離激元被分別聚焦為空心圈狀或?qū)嵭狞c(diǎn)狀分布。得益于石墨烯等離激元的可調(diào)諧性,在不影響分析儀工作特性的前提下,分析儀的工作波長(zhǎng)可以通過(guò)石墨烯費(fèi)米能級(jí)來(lái)加以調(diào)節(jié),并能夠?qū)崿F(xiàn)高達(dá)550的消光比。首次采用具有排列為螺旋型且指向方向互相垂直的兩列矩形納米金屬天線(xiàn)實(shí)現(xiàn)等離激元定向激發(fā)的方式來(lái)提升圓偏振分析儀的性能。在等離激元定向激發(fā)的作用下,圓偏振分析儀所實(shí)現(xiàn)的消光比將會(huì)被進(jìn)一步提升至103以上。5.首次提出六方氮化硼縫隙波導(dǎo)結(jié)構(gòu)并研究其縫隙區(qū)域支持的場(chǎng)增強(qiáng)效應(yīng),模式能量束縛效應(yīng)以及兩個(gè)六方氮化硼波導(dǎo)之間的梯度力現(xiàn)象。二維結(jié)構(gòu)的六方氮化硼縫隙波導(dǎo)可以實(shí)現(xiàn)接近于60的場(chǎng)增強(qiáng)因子,接近于80%的功率束縛因子以及-8.5 nN/μm×mW的梯度力,這大大高于基于傳統(tǒng)雙曲超材料的縫隙波導(dǎo)結(jié)構(gòu)。長(zhǎng)1 μm的三維縫隙波導(dǎo)結(jié)構(gòu)可以實(shí)現(xiàn)約為-1.2 nN/mW的梯度力以及約為50%的功率束縛因子。利用數(shù)值計(jì)算分析了在楔形石墨烯-六方氮化硼異質(zhì)結(jié)中存在的納米聚焦效應(yīng)。異質(zhì)結(jié)中存在的等離激元-聲子極化混合模式具有相對(duì)于雙曲聲子極化模式更小的模式損耗以及依賴(lài)于六方氮化硼平板波導(dǎo)厚度的色散特性。和楔形六方氮化硼波導(dǎo)相比,楔形異質(zhì)結(jié)能夠?qū)崿F(xiàn)高于60的歸一化場(chǎng)幅值的增強(qiáng)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.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TN256
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本文編號(hào)：1991189