Ultra-broadband toroidal metastructure absorber based on VO2 with enhanced anapole response

In recent years, metastructure absorbers have been developed rapidly. Broadband absorbers, serving as critical components in electromagnetic stealth applications and foundational elements for designing various functional absorbers, represent an important development in metastructure absorber research. Based on the significant near field enhancement effect of anapole modes, this study investigates the effectiveness in broadening absorption bandwidth and simplifying absorber structures of anapole mode. A waveguide-like ultra-wideband metastructure absorber (WUMA), based on toroidal metastructure design principles, is proposed. The results demonstrate that the designed WUMA achieves absorption rates exceeding 90% across 0.334 THz to 33.4 THz, with remarkable performance metrics including 196% fractional bandwidth and a linear octave ratio (the ratio of upper cutoff frequency to lower one) of 100. Simultaneously, it maintains over 10 dB radar cross section reduction throughout nearly its entire operational bandwidth. This design of WUMA establishes a novel paradigm for ultra-broadband absorbers, exhibiting significant potential for applications in electromagnetic stealth, electromagnetic compatibility, and advanced radar systems.