基于表面等离子激元理论提出一个由金属-介质-金属波导和半环切口组成的波导结构,应用时域有限差分法研究了该结构的透射特性.仿真结果表明：透射光谱中产生一个类似法诺共振线形的共振谷, 该法诺共振由半环切口中连续态与离散态的相互干涉所致, 其共振波长可以通过改变半环切口的结构参量进行调节, 该结构灵敏度约为575 nm/RIU, 品质因数可达5 671.添加一个矩形谐振腔于该结构上可产生多重法诺共振, 品质因数为6 555, 此特征能为波导结构的设计提供极大的灵活性,有望在光学集成回路、纳米传感器方面得到比较广泛的应用.

Based on the theory of Surface plasmon polaritons, a plasmonic structure consisting of a metal-insulator-metal waveguide and a semi-ring stub was proposed to investigate the transmission properties by the finite-difference time-domain method. Simulation results show that there is a sharp and asymmetric Fano profile in transmission spectrum, which originates from the interference between a discrete state and a continuous state in the semi-ring stub. The tuning of the Fano profile is realized by changing the size of the semi-ring stub, and the sensitivity and figure of merit of this structure is 575 nm/RIU and 5 671. Moreover, multiple fano resonances are induced by setting a rectangular cavity in the waveguide, a figure of merit as high as 6 555, which offer flexibility in the design of the structure. The waveguide structure may find widespread applications in highly integrated optical circuits, special for nano bio-sensor.