3-5 μm Mid-Infrared Broadband Perfect Absorber Based on Ti Ring Embedded Structure

Abstract

In this work, a 3-5 μm mid-infrared broadband perfect absorber is proposed. The proposed absorber is only composed of an aluminium oxide (Al2O3) dielectric layer on the top, a silicon (Si) dielectric layer with an embedded titanium (Ti) ring in the middle and a high loss metal substrate. It exhibits an extremely perfect absorption performance in the entire range of 3-5 μm mid-infrared band, with the highest and average absorption rates of 99.91% and 98.57%, respectively. The excellent absorption at 3-5 μm is attributed to the intrinsic absorption of the two dielectrics and the excitation of the surface plasmon resonance (SPR). Moreover, the average absorption rate can be still maintained above 91.33% when the incident angle of TE/TM or unpolarized wave reaches 60°, and there is almost unchanged in the absorption rate when the polarization angle of the incident wave gradually changes from 0° to 90°, which shows the insensitivity of the absorber to the incident and polarization angle. The absorber with simple structure and high stability has potential application prospects in infrared stealth and detection.

Keywords

• Mid-infrared
• embedded
• perfect absorber
• broadband
• surface plasmon resonance (SPR)