Performance optimization of hybrid gold-graphene metasurface infrared absorbers for dominant single-band response with dynamic resonance shifts

This paper presents the design, simulation, and analysis of an electrically tunable single-band infrared (IR) absorber featuring a periodic structure with gold metasurfaces and a graphene layer. The base structure consists of cross-shaped gold metasurfaces and a ground layer separated by an aluminum nitride (AlN) layer, optimized for narrowband absorption in the mid-IR range. A patterned graphene layer is added to enable electrical tunability. However, this layer not only slightly decreases the maximum absorption value but can also introduce additional peaks based on the graphene width, which is undesirable for our single-band absorber application. Optimization of graphene properties reveals an ideal width where the absorption spectrum transitions to a single narrowband response with maximum absorption. Furthermore, we apply plasmon hybridization theory to explain the physics of newly observed resonance, incorporating graphene, and examine the redshift in resonance frequencies resulting from changes in graphene's width. In addition, the absorber's performance is validated through an equivalent circuit model, confirming its tunability and efficiency. This study emphasizes the trade-offs between absorption efficiency, single-band response, and tunability, providing insights for designing highly sensitive, tunable IR sensors.