Breaking the symmetry to manipulate the magnetic Fano resonance in double split ring/square ring structure

Abstract

Optical properties of the Double Split Ring/Square Ring nanostructurre are investigated by using finite element method. Electric and magnetic resonances at optical frequency can be induced by this nanostructure. The symmetry of the structure is broken by adjusting the arm length of the double split ring and the offsets of the square ring, which leads the changing of inductance and capacitance. New magnetic resonances can be achieved and enhanced. Fano resonances are produced by the overlapping interference between bright electric mode and dark magnetic mode. The nanostructure allows the generation of multiple magnetic Fano resonances and strong magnetic field enhancement, which has potential applications in plasmons propagation with low-loss magnetic and multi-wavelength surface enhanced spectroscopy.