一种低损耗的对称双楔形太赫兹混合表面等离子体波导  

A symmetrical wedge-to-wedge THz hybrid SPPs waveguidewith low propagation loss

作　　者：王芳 张龙 马涛 王旭 刘玉芳[3] 马春旺[3] Wang Fang;Zhang Long;Ma Tao;Wang Xu;Liu Yu-Fang;Ma Chun-wang(College of Electronic and Electrical Engineering,Henan Normal University,Xinxiang 453007,China;Key Laboratory Optoelectronic Sensing Integrated Application of Henan Province,Henan Normal University,Xinxiang 453007,China;School of Physics,Henan Normal University,Xinxiang 453007,China)

机构地区：[1]河南师范大学电子与电气工程学院,新乡453007 [2]河南省光电传感集成应用重点实验室,新乡453007 [3]河南师范大学物理学院,新乡453007

出　　处：《物理学报》2020年第7期74-82,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61627818);河南省科技攻关项目(批准号:182102210367,182102310712);河南省高等学校重点科研项目(批准号:19A510002);河南师范大学国家级项目培育基金(批准号:2017PL04);河南师范大学博士启动课题(批准号:gd17167,5101239170010)资助的课题.

摘　　要：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.A symmetrical wedge-to-wedge THz hybrid SPPs waveguide(WWTHSW)with low propagation loss is investigated.The WWTHSW consists of two identical dielectric wedge waveguides symmetrically placed on each side of a micro wedge-patterned thin metal film.The mode characteristics of the WWTHSW,such as the propagation length(L_p),the normalized effective mode area(A)and the figure of merit(FOM)are analyzed by using the finite element method(FEM).Firstly,the influences of the height of Si micro wedge waveguide(H)and the gap between two wedges(g)on L_p and A are studied.For the same A first decreases and then increases with the increase of H.A achieves a minimum at an H of^40μm.However,L_p monotonically increases as H increases.The change of L_p slows down when H is greater than 40μm·At a fixed H,L_p slightly increases with the increase of g.But A achieves a minimum when g is^50 nm.Secondly,the dependencies of the mode characteristics of the WWTHSW on Si wedge tip angle(α)and Ag wedge tip angle(θ)are analyzed.At a fixedα,θhas less effect on L_p and A.Asαincreases at a fixedθ,L_p increases monotonically but A decreases firstly and then increases.A reaches a minimum whenαincreases to^100°.Then,the change of L_p and A with the thicknesses of Ag film(d)and Ag wedge(h)are demonstrated.At a fixed both L_p and A slightly decrease as d increases.For the same L_p and A decrease with the increase of h.A for h=0μm is distinctly larger than those for h=2μm and h=5μm.According to the above optimizations,the parameters of the WWTHSW are chosen as d=100 nm,g=50 nm,h=2μm,θ=80°,α=100°,H=40μm.Under the optimal parameters,L_p of^51 mm is obtained when reaches~λ~2/10280.Compared with the previous hybrid THz plasmonic waveguide,L_p of the WWTHSW increases by 3 times,and A decreases by an order of magnitude.This result reveals that the WWTHSW enables low-loss propagation and ultra-deep-subwavelength mode confinement at THz frequencies.At last,the coupling property of the parallel WWTHSW is investigated.The coupling length of^8

关 键 词：混合等离子波导 表面等离子体 传输特性 耦合特性 

分 类 号：O441.4[理学—电磁学] O53[理学—物理] TN814[电子电信—信息与通信工程]