Design of Ultra-Broadband Metamaterial Absorber in the Long-Wave Infrared Region Based on Impedance Matching
摘要
The infrared band occupies an extremely important position in the electromagnetic spectrum. The design of traditional infrared absorption devices relies on experience, which requires a large number of trial-and-error attempts and incurs substantial computational costs. In this paper, we adopt an impedance-matching-assisted design method to propose an ultra-broadband metamaterial absorber (MA) that can operate in the long-wave infrared band. This absorber features a two-layer silicon nitride (Si3N4) structure with embedded crisscrossed titanium (Ti) rectangles. The finite difference time domain (FDTD) method is used to analyze the absorption properties, which show that the proposed absorber absorbs more than 90% in the region from 7.1 µm to 16.5 µm, with an average absorption of 95% in the band from 7 µm to 17 µm. The MA exhibits polarization-insensitive properties as well as large angle absorption, with an average absorption of 87.8% and 85.8% for 60° incidence for the transverse magnetic (TM) and transverse electric (TE) modes. The absorption properties can be tuned by adjusting the parameters of the criss-crossed Ti rectangle. The broadband and high absorption properties of MA are mainly attributed to surface plasmon resonance (SPR), localized surface plasmon resonance (LSPR), cavity resonance, and their interactions. The proposed absorber with broadband and high absorption characteristics has potential applications in infrared imaging, infrared detection, and infrared communication. The impedance-matching-assisted design method, in contrast to the traditional trial-and-error approach, adjusts the absorber’s structural parameters based on the impedance matching effect. This approach holds significant importance for the rapid design of the absorber.