Broad spectrum attenuated total reflectance: numerical and experimental demonstration

Nano-optics is one of the most rapidly expanding fields in physics. Providing students with a basic knowledge of nano-optics and its practical applications, bridges the gap between theoretical concepts and real-world technological advancements, making the study of this branch of physics more tangible and exciting. In this study, we present a comprehensive analysis of the reflectivity of light from a thin-multilayered system across a broad spectrum. We theoretically examined the transmission and reflection of incident plane waves at interfaces between different media using the T-matrix method. We compared our theoretical findings with experimental results obtained from an attenuated total reflection (ATR) setup, which employed a supercontinuum laser as light source. This setup allowed us to observe both angular and spectral dependence of reflectivity. The sample under study, fabricated using e-beam physical vapor deposition, consisted of a BK-7 glass substrate, a 3 nm Cr layer, a 30 nm Au layer, and air as the superstrate. The obtained results demonstrate the accuracy of both, experimental and numerical methods. Our study not only serves as a valuable didactic resource, but also opens new perspectives for sensing applications where spectral shift of plasmonic resonances is a subject of interest. © 2025 Sociedad Mexicana de Fisica. All rights reserved.