  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.
