Aluminum Surface Lattice Resonances for Enhanced Near-Infrared Performance in Asymmetric Environments

Abstract

Aluminum (Al) is a cost-effective alternative to noble metals for plasmonics, particularly in the ul- traviolet (UV) and visible regions. However, in the near-infrared (NIR), its performance is hindered by interband transitions (IBTs) around 825 nm, leading to increased optical losses and broad res- onances. Surface lattice resonances (SLRs) offer a promising solution by enhancing the plasmonic quality factor (Q-factor) through coherent coupling of localized surface plasmon (LSP) modes with Rayleigh anomalies. Although high-Q SLRs have been demonstrated in homogeneous environments, achieving similar enhancements in asymmetric media such as air remains a challenge. This study presents a novel approach to improving the Q factor of aluminum in air by utilizing SLRs in aluminum nanoparticle (NP) arrays fabricated via electron beam lithography (EBL) on a high refractive index indium tin oxide (ITO) substrate. The ITO substrate enhances long-range coupling between NPs, reinforcing coherent interactions. Using absorption micro-spectrometry and finite-difference time- domain (FDTD) simulations, we demonstrate Q factors reaching 110 in air, significantly exceeding typical values in IR in assymmetrical surrounding medium. Our results establish aluminum as a viable low-cost material for high-performance plasmonic applications in sensing, telecommunications, and optoelectronics.