准周期的表面等离子体布拉格光栅的理论研究

Theoretical Study on Quasiperiodic Surface Plasmons Bragg Gratings

提出了一种基于金属-绝缘体-金属(MIM)波导结构的双频带表面等离子体(SPs)布拉格反射器。周期性地调节绝缘体层的宽度,在MIM波导结构中将会形成准周期的SPs布拉格光栅。根据投影理论,在合适的结构参数下,SPs的透过谱中会产生两个禁带,在这两个禁带中SPs的传播是被禁止的。加入适当长度的缺陷层之后,将分别在禁带中产生SPs缺陷模式,其中心波长分别是1310 nm和1550 nm。当改变缺陷层的长度时,由于SPs的法布里-珀罗共振效应,缺陷模式的中心波长会产生周期性的变化。利用电磁仿真软件Comsol进行数值模拟,得到的结果验证了设计方法的正确性。

A kind of dual- band surface plasmons（SPs） Bragg reflectors, based on metal- insulator- metal（MIM） waveguides, is proposed. By adjusting the width of the insulator layer periodically, a quasiperiodic SPs Bragg grating is achieved in the MIM waveguide structure. According to projection theory, transmission spectrum of SPs produces two band gaps, in which SPs′ propagation is prohibited under the suitable structure parameters. When inserting the defect layer of appropriate length into the structure, two SPs defect modes appear, whose center wavelengths are respectively located at around 1310 nm and 1550 nm. Because of the SPs Fabry- Perot effect, the center wavelengths of the defect modes change periodically as the change of defect layer length. The electromagnetic simulation is conducted by commercial software Comsol to verify the design.