Method for designing ultra-wideband absorbers based on water-filled Fabry-Perot cavity with continuously varying cavity length.

Abstract

Broadband and efficient terahertz (THz) absorbers are crucial for various applications in sensing, imaging, detecting, and modulation. Although recent studies have reported a series of THz metamaterials for enhanced absorption, achieving high absorption across the entire ultrabroad terahertz band remains challenging. We propose a novel, to the best of our knowledge, method to design ultra-wideband terahertz absorbers using a water-filled Fabry-Perot cavity with continuously varying cavity length. Our design achieves over 90% absorption across an ultrabroad terahertz band ranging from 0.26 to 30 THz. Furthermore, the design method can be extended to the visible, infrared, and microwave regimes. We believe that our method will inspire further studies and applications of ultra-wideband absorbers.