Ultra-Broadband, Tunable, and Transparent Microwave Meta-Absorber Using ITO and Water Substrate

Integrating broadband absorption, dynamic tunability, and high optical transparency into a single microwave absorber remains a crucial challenge. Here, an ultra-broadband, tunable, and transparent microwave meta-absorber comprising double-layer indium tin oxide resonant patterns and a water-based substrate is theoretically presented and experimentally demonstrated. Experimental measurements indicate that the designed meta-absorber can achieve over 90% absorption in an ultra-broadband frequency range of 12.49-98.21 GHz with a relative bandwidth of 154.9%, while the average optical transmittance is 60.49%. In addition, a multiple reflections interference model is employed to elucidate the physical mechanisms of the ultra-broadband absorber. Furthermore, its absorption performance can be reversibly switched between ultra-broadband and dual-broadband by altering the water substrate thickness. These peculiar properties make the proposed meta-absorber more favorable for practical applications in modern stealth materials and optical windows.