In this work, we propose a new approach regarding the characterization and the enhancement of transmitted light travelling inside a chitosan polymeric film improved by implementation of gold precursors generating nanocomposite materials. Firstly, the experimental optical characterization indicates the influence of the presence of gold particles on the effective refractive index of the chitosan polymer films and, secondly, the influence of their thickness supported by the transmittivity enhancement at precise frequencies for each gold precursor concentration and each polymer film thickness. This developed analysis introduces a basic study for the light enhancement in future complex photonic devices suitable for sensing.