Generation and manipulation of magnetic double Fano resonances in split asymmetric ring-disk nanostructure

摘要

As the basic geometric structure unit for generating surface plasmon, the split ring and the disk have been researched widely in both theory and experiment. A split asymmetric ring-disk (SAR-D) nanostructure is proposed to achieve both magnetic double Fano resonances and near field enhancement, which is investigated numerically based on the finite element method. In this nanostructure, Fano resonance is produced by the destructive interference between the bright electric mode and the dark magnetic mode. The extinction spectra can be modulated by changing the distance between the split asymmetric ring (SAR) and the disk, the thickness of the nanostructure and the radii of the SAR or the disk. Magnetic double Fano resonances can be excited effectively by rotation the SAR-D structure or splitting the disk along y-axis. Calculation results show that near field intensity is enhanced greatly at resonance peaks. Splitting the disk along y-axis, the strongest electric and magnetic field enhancements are achieved at the split gap, which are 386 and 118, respectively. This SAR-D nanostructure have potential applications in the surface enhance plasmon spectroscopy, the propagation of low-loss magnetic plasmons and the multiwavelength spectrometer.