Influence of refractive index, thickness and extinction coefficient on thin film reflectance

This study uses a theoretical and analytical approach based on comparative parameter variation to investigate the influence of thickness, refractive index, and extinction coefficient on the optical properties of thin films, with a particular focus on light reflection. Variations in thickness alter the number, position, and average reflectance of interference fringes. Changes in the refractive index affect fringe visibility, minimum reflectance, and fringe spacing. Meanwhile, the extinction coefficient primarily impacts the average reflectance while preserving the overall shape of the spectrum. To isolate and assess the specific effect of each parameter, a comparative method is employed in which one parameter is varied while the others are held constant. This approach enables a detailed investigation of the individual contributions of each variable. The objective is to understand and interpret the observed variations in the optical spectra, to identify the physical mechanisms responsible for these changes, and to determine which parameter has the most significant effect on reflection. The findings provide valuable insights into optimizing the optical behavior of thin films and offer a foundation for future advancements in optical material design for devices, sensors, and anti-reflective coatings.