Tunability in Graphene Based Metamaterial Absorber Structures in Mid-Infrared Region

• Published in: IEEE photonics journal 2022-06, Vol.14 (3), p.1-5
• Main Authors: Gupta, Shashank Kumar, Basu, Palash Kumar
• Format: Article
• Language: English
• Subjects: Absorber; Absorbers; Absorbers (materials); Absorption; Absorption spectra; Biosensors; Conductivity; Gas sensors; Graphene; Infrared radiation; Metals; Metamaterial; Metamaterials; Mid-infrared region; Optical surface waves; Polarization; Surface waves; Tunable; Tuning
• ISSN: 1943-0655; 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2022.3159447

Tunable conductivity of graphene, makes it a promising material for metamaterials. There are various graphene tunable metamaterial absorbers in the mid-infrared region, whose absorption spectrum can be dynamically tuned by varying the Fermi potential of graphene. However, graphene absorbers working in the low mid-infrared region (4-7 μm) has limited tuning. In this work, the spectral tuning efficiency of a graphene based metal disc pattern and a graphene ribbon pattern metamaterial absorber is studied using FDTD simulation. The tunability in absorption spectrum achieved by metal disc absorber is 2-4%, which increased to 5-20% for graphene ribbon absorber with more than 85% absorption rate. Thus, the graphene pattern absorber significantly improves the tunability and provides broad tuning in 4-7 μm wavelength range. However, the graphene ribbon absorber is polarization dependent due to its non-symmetric shape. Hence, a new type of nano square hole (NSH) graphene absorber is proposed, which can easily be externally biased and provide polarization independent absorption. The NSH graphene absorber has wide tunability of 5-20% and high absorption rate of 85% similar to the graphene ribbon absorber. These results are very helpful to design tunable sensors and multispectral devices for gas sensor and biosensor applications.