Design of Tunable Perfect Absorbers in the Mid-IR Spectrum Using Graphene-Based Multilayer Structures: Emerging Applications in Atmospheric Window Matching

This paper introduces tunable and switchable Perfect Absorbers (PAs) operating within the mid-infrared spectrum, specifically targeting the 3 to 5 um range at 0.25 um intervals. This spectrum is engineered for minimal atmospheric absorption and unique transmission characteristics. Our approach uses graphene-based nanophotonic aperiodic multilayer structures, optimized through micro-genetic algorithms within an inverse design framework. This combination broadens the design space, enabling highly accurate absorption control. Using the Transfer-Matrix-Method for simulations, we tailor absorption characteristics while keeping the structures under 2 um thick. Our results demonstrate PA tunability and switchability by adjusting graphene layers' chemical potentials. For instance, a 4 um peak can shift to 4.22 um by changing the graphene potential from 0 eV to 1 eV, without reducing efficiency. Our research also reveals PA adaptability to incident angles, maintaining 90% absorption up to 52 degrees, demonstrating versatility for applications like thermal photovoltaics, sensors, and stealth technology. This research deepens our understanding of nanophotonic materials and advances optical devices for the mid-IR range.