Analysis of novel optical properties of subwavelength double-layers metallic grating

We present a theoretical Fabry–Perot-Like model for the novel optical response of the subwavlength double-layers metal grating. The Fabry–Perot-Like resonance phenomenon has been found in this structure, and the complex cavities model is carried out for the interpretation of the resonant frequency shift due to the SPPs’ effect for the TM mode. The SPPs exist or not for TE and TM mode lead to different resonance frequency. We conclude that the reflection coefficient minimum corresponds to the condition satisfying the Fabry–Perot-Like resonance situation no matter for TE or TM mode.