对称纳米棒三聚体结构的Fano共振特性研究
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摘要
利用时域有限差分方法,理论研究了由中间短棒和两侧长棒构成的对称金纳米棒三聚体结构的光学性质,分析了结构参数和介电环境对其Fano共振特性的影响.结果表明:随着中间短棒长度、三棒整体尺寸或短棒两侧介质折射率的减小,Fano共振谷蓝移;棒间距的增大同样导致Fano共振谷蓝移,但边棒长度的变化对Fano共振谷位的影响较小;同时,随着纳米结构参数或介电环境的变化,Fano共振谷两侧共振峰强度发生改变,共振对比度先增大后减小.通过比较纳米结构截面的电磁场和电流密度矢量分布发现,共振谷两侧光谱强度的变化源于结构参数或介电环境引起的等离激元共振模式的改变.研究结果对基于Fano共振可控的纳米结构设计有一定的参考意义.
A symmetrical gold nanorod trimer structure consisting of a short center nanorod and two long nanorods on both sides is proposed.The scattering spectra,electromagnetic field and current density vector distributions across the central cross section of the nanorod trimer are calculated by the finite difference time domain method,and the effects of structural parameters and dielectric environment on Fano resonance characteristics are theoretically investigated in detail.The results show that the Fano resonance can be generated mainly due to the interference between the bonding electric dipole mode in lower energy and the antibonding electric dipole mode or antiphase magnetic dipole mode in higher energy.The Fano dip is blue-shifted with the decrease in the short nanorod length,the size of whole trimer structure with constant displacement,or the refractive index of dielectric medium in the gaps between the central nanorod and two side nanorods;the resonance intensity on both sides of the Fano dip also changes.Meanwhile,the bonding mode on the red side of the Fano dip is gradually dominated by the electric dipole mode of two side nanorods,and the spectral intensity increases,while the antibonding mode on the blue side gradually evolves into the short nanorod-dominated antiphase magnetic dipole mode,and the spectral intensity becomes weaker.The increase in the inter-rod spacing also leads the Fano dip to be blue-shifted,and a similar change in the spectral intensity occurs on both sides of the Fano dip,due to the degeneration of bonding and antibonding modes caused by the decrease of near-field coupling between the short nanorod and two side nanorods,which finally degenerate into the electric dipole modes generated by the short nanorod or the two side nanorods,respectively.In addition,the Fano dip is insensitive to the change of the side nanorod length,but the relative resonance intensity on both sides of the Fano dip also changes.Furthermore,it is found that the spectral contrast ratio of the Fano resonance first increases and then decreases by varying the above-mentioned structural parameters or dielectric environment.These results are expected to be used for guiding the design of Fano controllable nanostructures and also for developing the applications of specific micro-nano photonics.
A symmetrical gold nanorod trimer structure consisting of a short center nanorod and two long nanorods on both sides is proposed.The scattering spectra,electromagnetic field and current density vector distributions across the central cross section of the nanorod trimer are calculated by the finite difference time domain method,and the effects of structural parameters and dielectric environment on Fano resonance characteristics are theoretically investigated in detail.The results show that the Fano resonance can be generated mainly due to the interference between the bonding electric dipole mode in lower energy and the antibonding electric dipole mode or antiphase magnetic dipole mode in higher energy.The Fano dip is blue-shifted with the decrease in the short nanorod length,the size of whole trimer structure with constant displacement,or the refractive index of dielectric medium in the gaps between the central nanorod and two side nanorods;the resonance intensity on both sides of the Fano dip also changes.Meanwhile,the bonding mode on the red side of the Fano dip is gradually dominated by the electric dipole mode of two side nanorods,and the spectral intensity increases,while the antibonding mode on the blue side gradually evolves into the short nanorod-dominated antiphase magnetic dipole mode,and the spectral intensity becomes weaker.The increase in the inter-rod spacing also leads the Fano dip to be blue-shifted,and a similar change in the spectral intensity occurs on both sides of the Fano dip,due to the degeneration of bonding and antibonding modes caused by the decrease of near-field coupling between the short nanorod and two side nanorods,which finally degenerate into the electric dipole modes generated by the short nanorod or the two side nanorods,respectively.In addition,the Fano dip is insensitive to the change of the side nanorod length,but the relative resonance intensity on both sides of the Fano dip also changes.Furthermore,it is found that the spectral contrast ratio of the Fano resonance first increases and then decreases by varying the above-mentioned structural parameters or dielectric environment.These results are expected to be used for guiding the design of Fano controllable nanostructures and also for developing the applications of specific micro-nano photonics.
引文
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[2]Biswas S,Duan J,Nepal D,Park K,Pachter R,Vaia R A2013 Nano Lett.13 6287
[3]Artar A,Yanik A A,Altug H 2011 Nano Lett.11 3694
[4]Wu D,Liu C,Liu Y,Yu L,Yu Z,Chen L,Ma R,Ye H 2017Opt.Lett.42 450
[5]Zhang J,Chen S,Wang J,Mu K,Fan C,Liang E,Ding P2018 Sci.Rep.8 740
[6]Limonov M F,Rybin M V,Poddubny A N,Kivshar Y S 2017Nat.Photon.11 543
[7]Chen J,Gan F,Wang Y,Li G 2018 Adv.Opt.Mater.61701152
[8]Huang C Y,Chang H C 2019 IEEE Photon.J.11 4800208
[9]Li G Z,Hu H J,Wu L 2019 Phys.Chem.Chem.Phys.217654
[10]Wu C,Khanikaev A B,Shvets G 2011 Phys.Rev.Lett.106107403
[11]Chang W S,Lassiter J B,Swanglap P,Sobhani H,Khatua S,Nordlander P,Halas N J,Link S 2012 Nano Lett.12 4977
[12]Yu Y,Xue W,Semenova E,Yvind K,Mork J 2017 Nat.Photon.11 81
[13]Hu H J,Zhang F W,Li G Z,Chen J Y,Li Q,Wu L J 2018Photon.Res.6 204
[14]Yang Z J,Hao Z H,Lin H Q,Wang Q Q 2014 Nanoscale 64985
[15]Huang Y H,Li P 2015 Acta Phys.Sin.64 207301(in Chinese)[黄运欢,李璞2015物理学报64 207301]
[16]Zhang Y,Jia T Q,Zhang H M,Xu Z Z 2012 Opt.Lett.374919
[17]Fu Y H,Zhang J B,Yu Y F,Lukyanchuk B 2012 ACS Nano6 5130
[18]Zhao W,Jiang Y 2015 Opt.Lett.40 93
[19]Yang Z J,Wang Q Q,Lin H Q 2013 Appl.Phys.Lett.103111115
[20]Zhang S,Genov D A,Wang Y,Liu M,Zhang X 2008 Phys.Rev.Lett.101 047401
[21]Wang J,Liu X,Li L,He J,Fan C,Tian Y,Ding P,Chen D,Xue Q,Liang E 2013 J.Opt.15 105003
[22]Dong Z G,Liu H,Xu M X,Li Tao,Wang S M,Zhu S N,Zhang X 2010 Opt.Express 18 18229
[23]Jin X R,Park J,Zheng H,Lee S,Lee Y,Rhee J Y,Kim K W,Cheong H S,Jang W H 2011 Opt.Express 19 21652
[24]Bozhevolnyi S I,Evlyukhin A B,Pors A,Nielsen M G,Willatzen M,Albrektsen O 2011 New J.Phys.13 023034
[25]Yang Z J,Zhang Z S,Zhang L H,Li Q Q,Hao Z H,Wang Q Q 2011 Opt.Lett.36 1542
[26]Kai G,Zhang Y L,Qian C,Fung K H 2018 Opt.Express 2611984
[27]Liu G D,Zhai X,Wang L L,Wang B X,Lin Q,Shang X J2016 Plasmonics 11 381
[28]Liu S D,Leong E S P,Li G C,Hou Y,Deng J,Teng J H,Ong H C,Lei D Y 2016 ACS Nano 10 1442
[29]Wang J,Fan C,He J,Ding P,Liang E,Xue Q 2013 Opt.Express 21 2236
[30]Li G,Li Q,Xu L,Wu L 2015 Plasmonics 10 1401
[31]Cong C,Wu D J,Liu X J 2011 Acta Phys.Sin.60 046102(in Chinese)[丛超,吴大建,刘晓峻2011物理学报60 046102]
[32]Taflove A,Hagness S 2000 Computational Electrodynamics:the Finite-Difference Time-Domain Method(Vol.2)(Boston:Artech House)pp75-85
[33]Johnson P B,Christy R W 1972 Phys.Rev.B 6 4370
[34]Halas N J,Lal S,Chang W S,Nordlander P 2011 Chem.Rev.111 3913
[35]Feng R,Qiu J,Liu L,Ding W,Chen L 2014 Opt.Express 22A1713
[36]Hu X,Huang Y,Yuan S,Liu Y,Jiao Z,Wang Y,Huang Q,Yu J,Xia J 2015 Plasmonics 10 1817