Relevance of linear and nonlinear optical properties of Erythrosine B thin films for photonic application

This study investigates the structural and optical properties of Erythrosine B thin films. The films were fabricated through thermal evaporation and annealed at 423, 473, and 523 K. X-ray diffraction revealed that the films were initially amorphous, but their amorphous nature decreased with annealing. Optical transmittance and reflectance were measured across a wavelength range of 190– 2500 nm. After annealing, the transmittance dropped from 75% (as-deposited) to 40% at around 520 nm. The optical band gap also narrowed, reducing from 1.67 to 1.40 eV at 523 K. The refractive index showed anomalous dispersion below 900 nm and normal dispersion above, with ε_∞ values increasing from 2.14 to 2.74 as the annealing temperature rose. Additionally, the third-order nonlinear optical susceptibility decreased with annealing, with higher values observed in the as-deposited films. These results suggest that Erythrosine B thin films have the potential for photonic and optoelectronic applications due to their adjustable optical properties and thermal stability.