my country's 3D ring magnetic resonance metamaterials have made progress
Toroidal moment (toroidal moment) is a kind of electromagnetic excitation generated by the current flowing along the meridian on the torus or the magnetic dipole moment connected end to end. Due to its weak strength, it is often covered by the electrode moment and the magnetic pole moment. It is difficult to be directly observed. It was not until 2010 that people realized the electromagnetic response dominated by dynamic ring magnetic pole moments in the microwave band by using metamaterial structures. The dynamic ring magnetic pole moment has the ability of electromagnetic energy localization and radiation suppression, so the factor ring magnetic pole moment has application value in the fields of plasmon laser, sensing, optical rotation, negative refractive index and other fields. However, in the high frequency band, due to the limitation of the material structure and spatial modulation ability, the realization of the toroidal magnetic pole moment resonance metamaterial with practical value still faces many difficulties.
In recent years, the Institute of Physics/Beijing National Laboratory for Condensed Matter Physics (Beijing National Laboratory for Condensed Matter Physics) Micromachining Laboratory has been committed to the research on the processing methods and device applications of 3D micro-nano structures. They invented a new method of strain-induced 3D micro-nano structure processing based on focused ion beams, which can fold one-dimensional and two-dimensional materials multiple times in different degrees to achieve nanostructure units in space, size, period and geometry. Large-area controllable processing with modifiable appearance.
Recently, Dr. Liu Zhe from the laboratory and researchers Li Junjie and Gu Changzhi have extended this folded 3D structured material from metal nanowires and nanofilms to metal/dielectric composite structures, using a transparent SiNx film as the skeleton and using focused ion beams. The strain-induced folding processing technology combines the micron-sized metal opening resonant ring structure in 3D space with different opening directions and spatial positions to obtain a 3D optical metamaterial with a degree of freedom. Under the excitation of incident light in the vertical direction, the metal resonance ring produces LC resonance, and the resonance modes of the resonance ring in different opening directions are coupled, resulting in a magnetic couple
The pole moments are connected end to end along the ring, forming a ring magnetic dipole resonance. The ring magnetic resonance is located in the mid-infrared band, and the quality factor reaches 20.78.
By analyzing the radiation energy spectrum of the magnetic dipole moment, they observed the value of TZ at the resonance frequency, which proved the existence of ring magnetic dipole resonance. In order to make the intensity of ring magnetic dipole radiation higher than that of electric and magnetic dipoles, they used obliquely incident TM waves for excitation. They found that as the incident angle increased, the TZ radiation component gradually increased, and at an incident angle of 75° Its radiation intensity exceeds that of electric and magnetic dipoles, while still maintaining a good quality factor. This result proves the possibility of using the folded 3D structure to realize the magnetic dipole resonance of the factor ring, and shows a wide range of application prospects in the fields of sensing and plasmon lasers.
