【摘要】 基于衍射原理和模耦合理论,提出了一种由亚波长介质光栅/金属-电介质-金属(metal-dielectric-metal,MDM)波导/周期性光子晶体组成的复合微纳结构.结合反射角谱深入分析了表面等离子激元的传输特性以及在固定波长下不同入射角时刻形成的双重Fano共振的产生机理.研究表明,双重Fano共振是由在亚波长介质光栅/MDM波导结合的上层结构中产生的独立可调的双离散态分别与在周期性光子晶体中形成的连续态相互耦合形成的.接着定量讨论了结构参数对双重Fano特性的影响,探究了双重Fano共振的演变规律.结果表明,改变结构参数可实现双Fano共振曲线和谐振角度之间的调谐,且在最优条件下,共振A区FR a和FR b的品质因数(figure of merit,FOM)可高达460.0和4.00×10~4,共振B区FR a和FR b的FOM值可高达269.2和2.22×10~4.该结构可为基于Fano共振的折射率传感器设计提供有效的理论参考.更多还原

【Abstract】 Based on the diffraction principle and the mode coupling theory,a composite micro-nano structure of subwavelength dielectric grating/metal-dielectric-metal(MDM) waveguide/periodic photonic crystal is proposed.Combined with the angle spectrum of reflection,the transmission characteristics of the surface plasmon polaritons and the generation mechanism of double Fano resonances at different incident angles and fixed wavelength are analyzed.The studies show that the physical mechanism of double Fano resonances is that the surface plasmon resonance generated at the interface of sub-wavelength dielectric grating and upper metal Ag film,and the waveguide mode resonance occurring in the MDM waveguide,provide the independently tunable double discrete states,under the condition of satisfying wave vector matching,which can be respectively coupled in the near field with the continuous state formed by the photonic band gap effect in the photonic crystal,thereby achieving the double Fano resonances.Then the influence of the structural parameters on the double Fano characteristics is analyzed quantitatively,and the evolution law of the double Fano resonances is explored by the change of the reflection spectra of resonance curves.The results show that the tuning between double Fano resonance curves and the resonance angles can be realized by changing the structural parameters.And under optimal conditions,the figure of merit(FOM) values of FR a and FR b in resonance A region can be as high as 460.0 and 4.00 × 10~4,and the FOM values of FR a and FR b in resonance B region can be as high as 269.2 and 2.22 × 10~4.The structure can provide an effective theoretical reference for designing the refractive index sensors based on Fano resonances.更多还原