發(fā)布時間：2018-01-11 08:32

  本文關(guān)鍵詞：金納米結(jié)構(gòu)等離激元透鏡的聚焦特性的研究　出處：《南京大學》2017年博士論文　論文類型：學位論文

  更多相關(guān)文章： 表面等離激元 透鏡 相位調(diào)控 亞波長聚焦 相長干涉 時域有限差分法

【摘要】：表面等離激元是一種特殊電磁場,可以由光和金屬表面自由電子相互作用而激發(fā)。它沿介質(zhì)和金屬表面?zhèn)鞑?高度局域于金屬和介質(zhì)表面,具有比激發(fā)光波長短的波長及獨特的場增強效應(yīng),因而引起很多研究者的興趣。利用表面等離激元可以實現(xiàn)突破衍射極限的光子器件。隨著微納光學理論研究的深入以及微加工制備技術(shù)的進步,基于表面等離激元的亞波長光子器件可滿足小型化和集成化的需求,在近年來得到極大的發(fā)展。其中,金屬納米結(jié)構(gòu)(孔、縫、槽及它們的組合)由于在空間場調(diào)控和亞波長聚焦上獨特的能力,引起了研究者們的特別關(guān)注。本文基于表面等離激元的基本理論,利用數(shù)值模擬方法研究了幾種單個及陣列狀金納米結(jié)構(gòu)等離激元透鏡的遠場超分辨亞波長聚焦行為,并對其物理機制進行了分析。本論文工作的主要創(chuàng)新如下:1.提出了一種介質(zhì)填充型二次柱面等離激元透鏡。該透鏡由二氧化硅填充金膜納米狹縫陣列組成,金膜的出射表面為二次柱面。表面等離激元在狹縫入口處激發(fā)并沿狹縫傳輸,在狹縫出口轉(zhuǎn)變?yōu)閹в幸欢ㄏ辔谎舆t的自由空間傳播的光波。通過對透鏡結(jié)構(gòu)參數(shù)的控制,可以調(diào)節(jié)來自各狹縫的光波間的相對相位,使它們在設(shè)定的焦點處進行相長干涉,從而實現(xiàn)聚焦效果。用時域有限差分法數(shù)值計算了二次柱面等離激元透鏡的聚焦特性。數(shù)值模擬結(jié)果表明,所設(shè)計的孔徑為2μm的透鏡,能夠?qū)崿F(xiàn)微米級焦距和焦深、且焦斑半高寬低至0.4倍波長的亞波長聚焦。該表面等離激元透鏡結(jié)構(gòu)簡單緊湊、尺寸小,有利于光子器件的集成。2.提出了一種基于單環(huán)納米孔陣列與雙同心槽金膜等離激元透鏡。它由一個單環(huán)納米孔陣列和二個包圍環(huán)孔陣列雙側(cè)的同心槽構(gòu)成,納米孔穿透金薄膜;這是一種特殊的對稱的結(jié)構(gòu),可以用圓偏振光照明來實現(xiàn)聚焦。以往的對稱結(jié)構(gòu),多用徑向偏振光照明,但徑向偏振光不易獲得,而且徑向偏振光并不能適用于所有的對稱結(jié)構(gòu)。本文所設(shè)計的這種對稱結(jié)構(gòu),用圓偏振光照明就可較好地實現(xiàn)遠場聚焦。通過數(shù)值計算,找到了從凹槽和納米孔發(fā)出的光之間的相位差與凹槽位置之間的關(guān)系,再通過線性擬合,確定了在實現(xiàn)指定焦距處聚焦所需的凹槽位置參數(shù)。時域有限差分數(shù)值模擬得到了這種等離激元透鏡的電場分布,呈現(xiàn)出明顯的遠場聚焦現(xiàn)象。計算結(jié)果表明這種等離激元透鏡能夠?qū)崿F(xiàn)中心軸對稱的亞波長緊聚焦效果,焦斑的半高寬小于半個照明光波長并且獲得長焦深,達到了用同心槽改善遠場聚焦的目的,其聚焦性能顯著優(yōu)于常規(guī)的單環(huán)納米孔結(jié)構(gòu)等離激元透鏡。我們還進一步研究了等離激元透鏡陣列中相鄰兩個等離激元透鏡間的聚焦相互作用,通過數(shù)值模擬找到了相鄰兩個等離激元透鏡間的距離對最終聚焦特性的影響規(guī)律,提供了一個改善等離激元透鏡陣列聚焦特性的新途徑。3.提出了一種基于雙橢圓孔陣列與多同心環(huán)槽的金膜等離激元透鏡。該透鏡是由多重同心槽和雙橢圓形納米孔陣列構(gòu)成的金屬薄膜結(jié)構(gòu),其中的橢圓形納米孔沿阿基米德螺旋線分布。設(shè)計的納米孔使得入射線偏振光與表面等離激元耦合并向同心環(huán)槽傳播,而環(huán)槽可以有效地散射表面等離激元使之在金膜出口表面處轉(zhuǎn)換成在自由空間可傳播的波,從而實現(xiàn)亞波長的聚焦。我們對等離激元透鏡的聚焦特性進行了理論和數(shù)值研究。該透鏡能產(chǎn)生有趣的超分辨和長焦深焦場,比如光針或光管。值得注意的是,該透鏡即使在線偏振光照明下也能產(chǎn)生中心對稱的焦斑。4.提出了一種基于單環(huán)納米孔陣列與三個同心環(huán)形狹縫的寬光譜金膜等離激元透鏡。設(shè)計了單個及陣列狀等離激元透鏡,單個透鏡為單環(huán)納米孔陣列和三個位于單環(huán)孔內(nèi)同心狹縫的金納米透鏡,納米孔和狹縫均穿透金薄膜;陣列狀透鏡是以單個透鏡為單元按不同陣列大小構(gòu)建而成。用較易獲得的圓偏振光照明;由時域有限差分法模擬得到等離激元透鏡及其陣列的電場分布,呈現(xiàn)明顯地遠場聚焦現(xiàn)象;實現(xiàn)了中心軸對稱亞波長聚焦。已報導的納米結(jié)構(gòu)等離激元透鏡存在一些缺點,例如,傳輸光場發(fā)散以及精心設(shè)計的納米結(jié)構(gòu)只對特定的波長聚焦。而本文所設(shè)計透鏡及其陣列可以實現(xiàn)寬光譜聚焦,本文透鏡雖是針對660 nm光波設(shè)計,但在560 nm-760 nm范圍內(nèi)對任一波長光波均可實現(xiàn)良好的遠場聚焦。通過分析瑞利-索末菲積分找到了"入射光波長越大,焦距越小。"的原因。進一步研究了陣列中相鄰兩個單元之間的聚焦相互作用;通過數(shù)值模擬找到了相鄰兩個單元之間距離、照明光工作波長及陣列大小對最終聚焦特性的影響規(guī)律;提供了一個設(shè)計符合實際需要的透鏡陣列的依據(jù)。
[Abstract]:Surface plasmon is a special electromagnetic field can be determined by the interaction between light and metal surface free electron excited. It along the dielectric and metal surface spread, highly localized in metal and dielectric surface, compared with the length of the excitation light wavelength and unique field enhancement effect, so it attracts many researchers interested in using surface. Plasmonic photonic devices can break the diffraction limit. With the in-depth study of micro nano optical theory and micro fabrication technology, surface plasmon polaritons sub wavelength devices can meet the requirements of miniaturization and integration based on the great development in recent years. Among them, the metal nano structure (hole, groove joints, and their combination) due to the regulation in the space field and sub wavelength focusing unique ability, particularly attracted the attention of researchers. In this paper, the basic theory of surface plasmon polaritons based on Li Study of several arrays and single shaped gold nanostructures plasmonic lens by numerical simulation method of far-field super-resolution subwavelength focusing behavior, and the physical mechanism is analyzed. The main contributions of this dissertation are as follows: 1. put forward a two cylindrical dielectric filled plasmonic lens. The the lens is made of silica filled gold film nanogap arrays of gold film exit surface for two times. The cylindrical surface plasmon in the entrance slit along the slit excitation and transmission, in the exit slit into the light with the free space propagation phase delay. By controlling the lens structure parameters, can adjust the relative phase the light from the slit between them, so long in the focal point set interference, so as to realize the focusing effect. Calculated the two cylinder focusing the plasmonic lens characteristics calculated by using FDTD . the numerical simulation results show that the designed lens aperture of 2 m, can achieve micron focal length and focal depth, subwavelength focusing and focal spot width as low as 0.4 times the wavelength of the surface plasmon. The lens has simple and compact structure, small size, have integrated photonic devices for.2. a plasmonic lens single ring nano hole array with dual concentric grooves on gold film based on. It consists of a single ring nano hole array and two ring hole surrounded by concentric array of bilateral grooves, nanoporous gold film penetration; this is a special kind of symmetrical structure, can be used circularly polarized light focusing is achieved. The symmetric structure in the past, with radially polarized illumination, but radially polarized light is not easy to get, and the radially polarized light and not applicable to all symmetric structure. The symmetric structure is designed in this paper, using circularly polarized lighting can achieve better far-field poly Coke. Through numerical calculation, find out the relationship between the phase between the groove and the hole from the poor and the position of the groove, and then through the linear fitting, groove position parameters in achieving the desired specified focal distance focusing was determined. The finite difference time domain numerical simulation to get the plasmonic lens field distribution, showing a far field focusing phenomenon obviously. The calculation results show that the effect of tightly focused subwavelength plasmonic lens can realize axis symmetry, half width of the focal spot is less than half of a wavelength of light illumination and long focal depth, to improve the far field focus on the purpose of using concentric groove, plasmonic lens the focusing performance is significantly better than the conventional single loop nano pore structure. We further studied the plasmon polaritons in adjacent lens array two plasmon lens focusing interaction, through the numerical simulation to find the phase Influence of two adjacent plasmonic lens and the distance between the final focusing characteristics, provides a new way of.3. plasmonic lens array focusing characteristics of an improvement, proposed a plasmonic lens double elliptical holes array and multiple concentric ring groove based on gold film. The lens is a metal film the structure is composed of a plurality of concentric grooves and double elliptic nano hole array, the oval nano hole along the Archimedes spiral line. The distribution of linearly polarized light with surface plasmon coupling and concentric ring groove to spread nano hole design makes, and the ring groove can effectively scattering surface plasmon to export in the gold film surface can be converted into the wave propagation in free space, so as to realize the sub wavelength. We focus on equivalence focusing properties of plasmonic lens are studied theoretically and numerically. The lens can produce high resolution and long focal depth and focal field interesting For example, light or light pipe. It is worth noting that, even if the lens focal spot.4. online under polarized illumination can also produce symmetrical presents a single ring nano hole array based on three concentric ring slit wide spectrum of gold film plasmonic lens. The design of single and array plasmon element lens, a single lens is a single ring nano hole array and three in single hole concentric ring slit gold nano lens, nano hole and slit are penetrating the gold thin film; array lens is formed by a single lens unit is constructed. According to the different array size obtained by circularly polarized light lighting is easy; simulation etc. from the electric field excitation lens and lens array distribution by FDTD method, showing obviously far field focusing phenomenon; the central axis symmetric subwavelength focusing. Reported nanostructured plasmonic lens has some shortcomings, for example, light field The divergence and nano structure carefully designed only for specific wavelength. And the design of focusing lens and lens array can achieve a wide spectrum of focus, this paper is aimed at the 660 nm optical lens design, but the realization of far field focusing on any good wavelength wave can be 560 nm-760 in the range of nm. Through the analysis of the Rayleigh Sommerfeld integral find the wavelength of incident light increases, the smaller focal length. The reason. To further study the interaction between the two adjacent unit array focusing; through numerical simulation to find the distance between the two adjacent unit, influence of wavelength and light illumination on the final size of array focusing characteristics; provides a design to meet the according to the actual needs of the lens array.

【學位授予單位】：南京大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB383.1;O441

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本文編號：1408864