摘要： Poly (ethyl methacrylate) (PEMA) - cellulose acetate propionate (CAP) blend film was prepared using the cast technique. A Q-switched Nd: YAG laser beam with a wavelength of 266 nm, a pulse duration of 10-ns, a repetition rate10 Hz and 0.018 J/cm2 fluence was used to irradiate the prepared film. The optical absorption of pristine and irradiated sample was studied within 200–500 nm wavelength region. The absorbance increases with laser irradiation time over the full wavelength region which is attributed to an increase of the crosslinking network. Examining Tauc plots revealed a transition of the direct allowed type with optical energy gap value of 4.92 eV for the pristine blend film which has decreased to 4.30 eV after laser irradiation for 90 min. The refractive index, finesse coefficient, dielectric function, Brewster, and critical angles demonstrated dispersion in the 200–500 nm wavelength range.