本文關鍵詞： THz波導 模場寬度 模式損耗 表面等離激元　出處：《深圳大學》2017年碩士論文　論文類型：學位論文

【摘要】：太赫茲(Terahertz,簡稱THz)波是指頻率在0.1~1 THz范圍內(nèi)的電磁波,位于紅外與微波之間,處于宏觀電子學向微觀電子學的過渡階段,因而具有許多獨特的性質(zhì)。在基礎物理科學、超高速通信、高分辨率成像、安全檢查、無損檢測等方面具有重要的研究價值和廣泛的應用前景。但目前缺乏低損耗、長距離傳輸?shù)牟▽沟锰掌澋膽檬艿胶艽笙拗?開發(fā)低損耗、小模場的太赫茲波導對于推動太赫茲技術的實際應用具有十分重要的意義。由于現(xiàn)有的波導普遍存在低損耗與小模場難以同時實現(xiàn)的問題,由此,本文對傳統(tǒng)波導的結構和材料進行可行性改進,分別提出了置于介質(zhì)孔內(nèi)的納米金屬線、石墨烯包裹的水滴狀延拓納米線、金屬-縫隙-介質(zhì)對稱型波導,并利用數(shù)值分析軟件與基于有限元方法的COMSOL商用軟件研究了它們的傳導特性。首先,利用COMSOL軟件對置于介質(zhì)孔內(nèi)的金屬線的表面等離激元模式進行仿真研究,并能與數(shù)值計算結果相互呼應。理論上很好地證明了置于介質(zhì)孔內(nèi)的金屬線可以保持模式寬度與單金屬線基本一致的情況下,將損耗降至極低。其主要原因是引入足夠大的介質(zhì)孔能夠改變部分模場,在維持模式寬度基本不變的前提下,使得集中在金屬線內(nèi)的場能減小,從而縮小傳輸損耗。在工作頻率為0.3 THz時,金屬線半徑為100 nm,損耗的理論值非常小,為0.42 m~(-1),同時模場寬度僅為納米量級(290 nm)。其次,提出了利用石墨烯包裹的水滴狀延拓納米線傳導THz表面等離激元。我們采用在太赫茲頻段具有類金屬性質(zhì)的石墨烯材料包裹在水滴狀延拓納米線外,利用COMSOL求解,結果發(fā)現(xiàn),該波導可以大大降低模式寬度。在工作頻率為3 THz,底弧R為1μm時,在波導的楔形頂角出現(xiàn)寬度很小的亮斑,模式寬度為34 nm,其傳輸損耗為1.3 mm~(-1),即傳播長度近800μm(相當于7λ0)。即該波導在保證傳輸損耗較低的前提下,實現(xiàn)了納米聚焦。最后,提出金屬-縫隙-介質(zhì)對稱型波導,主要包括兩種類型:平板型和柱型,主要是利用插入電介質(zhì)的方法改變了金屬平板(或者金屬空芯管)的模場特點。我們分別通過理論推導出TE模、TM模與HE模的色散方程。從數(shù)值計算結果直觀地發(fā)現(xiàn),模場更集中在介質(zhì)層內(nèi),在模場寬度不增大的前提下,這種波導可以實現(xiàn)超低損耗傳輸THz波。當f為0.5 THz,平行平板DGM波導中兩個金屬層間距為b=λ/2時,TE1模和TM1模的最小損耗分別為0.21 m~(-1)和0.17 m~(-1);對于柱狀DGM波導,金屬銅管(內(nèi)環(huán))直徑為2λ/3時,HE11模的最小損耗為0.20 m~(-1)。與不插入電介質(zhì)的波導相比,它們的損耗均可以下降1~3個數(shù)量級。
[Abstract]:Terahertz (THz) waves are electromagnetic waves with a frequency of 0.1 THz, between infrared and microwave. At the stage of transition from macroelectronics to microelectronics, it has many unique properties. In basic physics science, ultra-high speed communication, high resolution imaging, security inspection. Nondestructive testing (NDT) has important research value and wide application prospect. However, the lack of low loss and long distance transmission waveguide make the application of terahertz to be greatly limited, and the development of low loss. THz waveguides with small mode field are of great significance to promote the practical application of THz technology. Because the existing waveguides are generally low loss and small mode field difficult to achieve at the same time. In this paper, the structure and materials of traditional waveguides are improved. Nanowires, water droplet extension nanowires, metal-crevice dielectric symmetric waveguides, which are placed in dielectric holes, are proposed respectively. Numerical analysis software and COMSOL commercial software based on finite element method are used to study their conduction characteristics. First of all. COMSOL software is used to simulate the surface of the metal wire in the dielectric hole. It is proved in theory that the metal wire placed in the dielectric hole can keep the mode width basically consistent with the single metal wire. The main reason is that the medium hole can change part of the mode field, and the field energy concentrated in the metal wire can be reduced under the premise of maintaining the mode width basically unchanged. Thus, the transmission loss is reduced. When the operating frequency is 0.3 THz, the wire radius is 100nm.The theoretical value of the loss is very small, which is 0.42 mm2 ~ (-1). At the same time, the width of the mode field is only about 290 nm ~ (-1) nanoscale. Water droplet extension nanowires coated with graphene were proposed to conduct isoexcitons on THz surface. Graphene materials with metal-like properties in terahertz band were used to encapsulate water droplet continuation nanowires. Using COMSOL solution, it is found that the mode width of the waveguide can be greatly reduced. When the operating frequency is 3 THZ and the bottom arc R is 1 渭 m, a small width bright spot appears in the wedge top angle of the waveguide. The mode width is 34 nm and the transmission loss is 1.3 mm / L, that is, the propagation length is nearly 800 渭 m (equivalent to 7 位 0), that is, the transmission loss of the waveguide is low. Finally, the metal-crevice dielectric symmetrical waveguide is proposed, which includes two types: plate type and column type. The mode field characteristics of metal plate (or metal hollow tube) are changed by the method of inserting dielectric. The dispersion equations of TM mode and HE mode. From the numerical results, it is found that the mode field is more concentrated in the dielectric layer and the width of the mode field does not increase. The ultra-low loss THz wave can be transmitted by this waveguide. When f is 0. 5 THZ, the distance between the two metal layers in the parallel plate DGM waveguide is b = 位 / 2:00. The minimum loss of TE1 mode and TM1 mode are 0.21 m-1 and 0.17 mG-1, respectively. For a cylindrical DGM waveguide, the minimum loss of the metallic copper tube (inner ring) is 0.20 m / m ~ (-1) in diameter of 2 位 / 3:00 ~ (-1) H _ (11) mode, compared with the waveguide without dielectric insertion. Their losses can be reduced by 1 ~ 3 orders of magnitude.
【學位授予單位】：深圳大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN814

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