Influence of UV irradiation on the structural and optical properties of Ch-HPQ thin films

The influence of ultraviolet (UV) irradiation on the structural, linear optical and non-linear optical properties of
2-Amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3,2-c] quinoline-3-carbonitrile (Ch-HPQ)
thin films is elaborated. The morphology of the UV irradiated, for different irradiation times, Ch-HPQ thin films is
studied using both scanning electron microscopy and X-ray diffraction and compared with the UV non irradiated
one. The transmittance and reflectance spectra of Ch-HPQ thin films are studied based on spectrophotometric
measurements in the spectral range (200–2500) nm. Several parameters (e.g. the molar extinction coefficient, the
onset and optical energy gap values) are calculated from the absorption spectra. Dispersion of the studied ma-
terial is explained by Wemple and Di Domenico single-oscillator model. The influence of UV irradiation on the
loss functions is discussed. The theoretical calculations of the non-linear optical parameters such as third order
non-linear susceptibility and the non-linear refractive index are investigated from linear optical parameters using
semi-empirical relations. The homogeneity of Ch-HPQ thin films are found to be stable under the UV irradiation
which recommends using this material in optoelectronic applications.