Near-Perfect Infrared Absorption in Atomic Monolayers: Approaching the Fundamental Optical Limit

Abstract High absorption in the mid-infrared band is essential for applications ranging from information processing to energy harvesting. Conventionally, achieving broadband absorption approaching the optical limit has required absorber thicknesses comparable to or exceeding the characteristic wavelength. By contrast, realizing such broadband infrared absorption at the atomic scale has remained exceedingly difficult. In this work, we demonstrate that one- dimensional MXene grating system provides a platform for achieving strong infrared absorption at atomic thicknesses. The results show that an 8 nm MXene film (~ λ /1000) patterned with a simple stripe grating is found to approach the theoretical absorption limit of 0.5 for two-dimensional films. The absorption peak wavelength is readily tuned by varying the MXene strip width, while the positions of the optical resonances are accurately captured by a Fabry-Pérot model. Power dissipation analysis further reveals that the absorption arises from resonance-driven field enhancement and establishes a direct correlation between absorption and grating periodicity. These findings demonstrate a viable strategy for atomic-scale control of thermal radiation through rationally designed nanostructures.