The Coupling Effects of Surface Plasmon Polaritons and Magnetic Dipole Resonances in Metamaterials

Nanoscale Research Letters, Nov 2017

We numerically investigate the coupling effects of surface plasmon polaritons (SPPs) and magnetic dipole (MD) resonances in metamaterials, which are composed of an Ag nanodisk array and a SiO2 spacer on an Ag substrate. The periodicity of the Ag nanodisk array leads to the excitation of SPPs at the surface of the Ag substrate. The near-field plasmon interactions between individual Ag nanodisks and the Ag substrate form MD resonances. When the excitation wavelengths of SPPs are tuned to approach the position of MD resonances by changing the array period of Ag nanodisks, SPPs and MD resonances are coupled together into two hybridized modes, whose positions can be well predicted by a coupling model of two oscillators. In the strong coupling regime of SPPs and MD resonances, the hybridized modes exhibit an obvious anti-crossing, resulting into an interesting phenomenon of Rabi splitting. Moreover, the magnetic fields under the Ag nanodisks are greatly enhanced, which may find some potential applications, such as magnetic nonlinearity.

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The Coupling Effects of Surface Plasmon Polaritons and Magnetic Dipole Resonances in Metamaterials

Liu et al. Nanoscale Research Letters The Coupling Effects of Surface Plasmon Polaritons and Magnetic Dipole Resonances in Metamaterials Bo Liu 1 3 5 Chaojun Tang 1 2 3 Jing Chen 0 1 3 4 6 7 0 College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications , Nanjing 210023 , China 1 Equal contributors 2 Center for Optics and Optoelectronics Research, Collaborative Innovation Center for Information Technology in Biological and Medical Physics, College of Science, Zhejiang University of Technology , Hangzhou 310023 , China 3 , Zhendong Yan 4 , Yongxing Sui 5 School of Mathematics and Physics, Jiangsu University of Technology , Changzhou 213001 , China 6 National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University , Nanjing 210093 , China 7 State Key Laboratory of Millimeter Waves, Southeast University , Nanjing 210096 , China We numerically investigate the coupling effects of surface plasmon polaritons (SPPs) and magnetic dipole (MD) resonances in metamaterials, which are composed of an Ag nanodisk array and a SiO2 spacer on an Ag substrate. The periodicity of the Ag nanodisk array leads to the excitation of SPPs at the surface of the Ag substrate. The near-field plasmon interactions between individual Ag nanodisks and the Ag substrate form MD resonances. When the excitation wavelengths of SPPs are tuned to approach the position of MD resonances by changing the array period of Ag nanodisks, SPPs and MD resonances are coupled together into two hybridized modes, whose positions can be well predicted by a coupling model of two oscillators. In the strong coupling regime of SPPs and MD resonances, the hybridized modes exhibit an obvious anti-crossing, resulting into an interesting phenomenon of Rabi splitting. Moreover, the magnetic fields under the Ag nanodisks are greatly enhanced, which may find some potential applications, such as magnetic nonlinearity. Metamaterials; Plasmonics; Surface plasmon polaritons; Magnetic dipole resonances; Magnetic field enhancement Background It is well known that naturally occurring materials exhibit the saturation of the magnetic response beyond the THz regime. In light-matter interactions at optical frequencies, the magnetic component of light generally plays a negligible role, because the force exerted by the electric field on a charge is much larger than the force applied by the magnetic field, when light interacts with matter [ 1 ]. In the past few years, developing various metallic or dielectric nanostructures with appreciable magnetic response at optical frequencies has been a matter of intense study in the field of metamaterials. Recently, there is increasing interest in optical magnetic field characterization in nanoscale, although it remains a challenge because of the weak matter-optical magnetic field interactions [ 2 ]. At the same time, there have also been many efforts to obtain strong magnetic response with magnetic field enhancement in a wide spectrum range from visible [ 3–22 ] to infrared [ 23–44 ] regime. The physical mechanism underlining strong magnetic response is mainly the excitation of MD resonance in a variety of nanostructures including metal-insulator-metal (MIM) sandwich structures [ 3, 12, 16, 31, 32, 40 ], metallic split-ring resonators [ 29, 30, 36, 41, 42 ], high-refractiveindex dielectric nanoparticles [ 14, 15, 17, 18, 20, 21 ], plasmonic nanoantennas [ 6, 8, 24–26, 28, 34, 37, 43 ], metamolecules [ 7, 9, 11, 13, 19, 33, 35, 38 ], and so on. To obtain strong magnetic response with magnetic field enhancement, MD resonance is also coupled to different narrow-band resonance modes with a high-quality factor, e.g., surface lattice resonances [ 4, 22, 39, 44 ], Fabry-Pérot cavity resonances [ 10, 23 ], Bloch surface waves [5], and Tamm plasmons [ 27 ]. A strong magnetic response with a great enhancement of magnetic fields at optical frequencies will have many potential applications, such as MD spontaneous emission [ 45–52 ], magnetic nonlinearity [ 53–56 ], optically controlled magnetic-field etching [ 57 ], magnetic optical Kerr effect [ 58 ], optical tweezers based on magneticfield gradient [ 59, 60 ], circular dichroism (CD) measurement [61], etc. It is well known that plasmonic electric dipole resonance can hugely enhance electric fields in the vicinity of metal nanoparticles, and its coupling to SPPs can further enhance electric fields and generate other interesting physical phenomena. However, there are only a few researches on the coupling effects of SPPs and MD resonances. In this work, we will numerically demonstrate the huge enhancement of magnetic fields at optical frequencies and the interesting phenomenon of Rabi splitting, due to the coupling effects of SPPs and MD resonances in metamaterials composed of an Ag nanodisk array and a SiO2 spacer on an Ag substrate. The near-f (...truncated)


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Bo Liu, Chaojun Tang, Jing Chen, Zhendong Yan, Mingwei Zhu, Yongxing Sui, Huang Tang. The Coupling Effects of Surface Plasmon Polaritons and Magnetic Dipole Resonances in Metamaterials, Nanoscale Research Letters, 2017, pp. 586, Volume 12, Issue 1, DOI: 10.1186/s11671-017-2350-z