Ultranarrow and Tunable Fano Resonance in Ag Nanoshells and a Simple Ag Nanomatryushka
Ping Gu,
Xiaofeng Cai,
Guohua Wu,
Chenpeng Xue,
Jing Chen,
Zuxing Zhang,
Zhendong Yan,
Fanxin Liu,
Chaojun Tang,
Wei Du,
Zhong Huang,
Zhuo Chen
Affiliations
Ping Gu
Institute of Advanced Photonics Technology, College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Xiaofeng Cai
Institute of Advanced Photonics Technology, College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Guohua Wu
Institute of Advanced Photonics Technology, College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Chenpeng Xue
Institute of Advanced Photonics Technology, College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Jing Chen
Institute of Advanced Photonics Technology, College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Zuxing Zhang
Institute of Advanced Photonics Technology, College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Zhendong Yan
College of Science, Nanjing Forestry University, Nanjing 210037, China
Fanxin Liu
College of Science, Zhejiang University of Technology, Hangzhou 310023, China
Chaojun Tang
College of Science, Zhejiang University of Technology, Hangzhou 310023, China
Wei Du
College of Physics Science and Technology, Yangzhou University, Yangzhou 225002, China
Zhong Huang
College of Physics and Electronic Engineering, Jiangsu Second Normal University, Nanjing 210013, China
Zhuo Chen
National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093, China
We study theoretically the Fano resonances (FRs) produced by the near-field coupling between the lowest-order (dipolar) sphere plasmon resonance and the dipolar cavity plasmon mode supported by an Ag nanoshell or the hybrid mode in a simple three-layered Ag nanomatryushka constructed by incorporating a solid Ag nanosphere into the center of Ag nanoshell. We find that the linewidth of dipolar cavity plasmon resonance or hybrid mode induced FR is as narrow as 6.8 nm (corresponding to a high Q-factor of ~160 and a long dephasing time of ~200 fs) due to the highly localized feature of the electric-fields. In addition, we attribute the formation mechanisms of typical asymmetrical Fano line profiles in the extinction spectra to the constructive (Fano peak) and the destructive interferences (Fano dip) arising from the symmetric and asymmetric charge distributions between the dipolar sphere and cavity plasmon or hybrid modes. Interestingly, by simply adjusting the structural parameters, the dielectric refractive index required for the strongest FR in the Ag nanomatryushka can be reduced to be as small as 1.4, which largely reduces the restriction on materials, and the positions of FR can also be easily tuned across a broad spectral range. The ultranarrow linewidth, highly tunability together with the huge enhancement of electric fields at the FR may find important applications in sensing, slow light, and plasmon rulers.
