一维金属光栅的光学反射吸收

利用RCWA(rigid coupled-wave analysis)方法研究了一维金属光栅的反射特性,考察了 瑞利反常、表面等离激元驻波共振和几何共振三种共振吸收机理,分析了这三种机理的相互作用,如表面等离激元驻波共振和几何共振可以形成混合模式. 在反射式复合金属光栅中,确认了第四种共振形式,即相位共振. 数值计算表明相位共振对光学吸收的影响有两种形式: 当光栅周期大于一个波长时,相位共振导致尖锐的吸收峰,峰位在几何共振吸收峰一侧;当光栅周期小于一个波长时,相位共振导致混合模式的共振吸收峰发生劈裂. 对一维金属光栅反射特性的研究增加了对金属光栅共振吸收模式及其相互作用的认识. 关键词： 一维金属光栅 瑞利反常 表面等离激元 相位共振

Numerical study on the optical absorption of one dimension metallic gratings

We investigate the reflected response of one-dimensional metallic grating with rigid coupled-wave analysis. Three types of resonance absorptions, i.e., Rayleigh anomaly, surface plasmon polariton (SPP) standing wave resonance and geometric resonance, are identified in the gray-scale map of the reflectivity as a function of two structural parameters: grating period and groove depth. Furthermore, the interactions among these resonances are discussed. Our calculation reveals that a hybrid mode of SPP standing wave resonance and geometric resonance can be found, while no hybrid mode of Rayleigh anomaly and geometric resonance exists. In the analysis of compound gratings, we find phase resonance. How the phase resonance changes the reflection and the absorption of compound metallic gratings is also discussed. When the wavelength of incident light is less than grating period, sharp dip is found in reflectivity as a function of groove depth. In the other case, i.e. Wavelength greater than grating period, phase resonance results in a split of the hybrid absorption branch of SPP standing wave resonance and geometric resonance.