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)