A Near-Infrared Multi-Band Perfect Absorber Based on 1D Gold Grating Fabry-Perot Structure

In recent years, multi-band perfect absorbers have great advantages in spectroscopy, infrared detection and other fields. Here we propose and use the finite-difference time-domain (FDTD) method to numerically calculate the multi-band absorber based on 1D gold grating Fabry-Perot (FP) structure. The full-wave simulation results show that under normal incident conditions, four different absorption peaks can be obtained in the near-infrared band and the absorption is all close to 1. These resonance peaks are derived from the third-, fourth-, fifth-, and sixth-order resonances of mode coupling in the FP cavity, respectively. The narrowest absorption bandwidth is 24 nm and the quality factor is 37.6. By adjusting the structural parameters of the grating, its spectrum can be adjusted and selected, and its working angle tolerance can reach 50°. In addition, numerical results show that the absorber can detect slight changes in the environment when used as a sensor. Therefore, our absorber has potential applications in the field of sensor detection.