Ultrathin and Electrically Tunable Metamaterial with Nearly Perfect Absorption in Mid-Infrared

• Main Authors: Yuexin Zou, Jun Cao, Xue Gong, Ruijie Qian, Zhenghua An
• Format: Article
• Language: English
• Published: MDPI AG 2019-08-01
• Series: Applied Sciences
• Subjects: metamaterial; perfect absorber; graphene; coupled-mode theory; tunable device
• Online Access: https://www.mdpi.com/2076-3417/9/16/3358

Metamaterials integrated with graphene exhibit tremendous freedom in tailoring their optical properties, particularly in the infrared region, and are desired for a wide range of applications, such as thermal imaging, cloaking, and biosensing. In this article, we numerically and experimentally demonstrate an ultrathin (total thickness <inline-formula> <math display="inline"> <semantics> <mrow> <mo>&lt;</mo> <msub> <mi mathvariant="sans-serif">&#955;</mi> <mn>0</mn> </msub> <mo>/</mo> <mn>15</mn> </mrow> </semantics> </math> </inline-formula>) and electrically tunable mid-infrared perfect absorber based on metal&#8722;insulator&#8722;metal (MIM) structured metamaterials. The Q-values of the absorber can be tuned through two rather independent parameters, with geometrical structures of metamaterials tuning radiation loss (Q_r) of the system and the material loss (tan&#948;) to further change mainly the intrinsic loss (Q_a). This concise mapping of the structural and material properties to resonant mode loss channels enables a two-stage optimization for real applications: geometrical design before fabrication and then electrical tuning as a post-fabrication and fine adjustment knob. As an example, our device demonstrates an electrical and on-site tuning of ~5 dB change in absorption near the perfect absorption region. Our work provides a general guideline for designing and realizing tunable infrared devices and may expand the applications of perfect absorbers for mid-infrared sensors, absorbers, and detectors in extreme spatial-limited circumstances.