Low-intensity UV effects on optical constants of PMMA film

Effects of low-intensity UV treatment on theoptical constants of red BS dye-doped polymethyl methacrylate(PMMA) film including refractive index, extinctioncoefficient, real and imaginary parts of dielectricconstant, band gap energy, Urbach energy, and refractiveindex dispersion parameters are measured and calculated.Changes in optical constants mainly occurred in the UV–VIS range. Red BS dye, which is used as a UV absorberimpurity in PMMA films, generated another energy bandgap which was increased by UV treatment. Although someof the optical constants of PMMA are not changednoticeably by the treatment in this low range of UV radiation,our results confirm that polymeric changes such aschain scission and depolymerization can directly affect theoptical constants of PMMA.