Optical properties of ZnSe film under 532 nm laser irradiation

The ZnSe thin films were manufactured by electron beam thermal evaporation technique and the whole changes were studied in transmittance, refractive index, extinction coefficient and laser-induced damage threshold (LIDT) of ZnSe thin films under the laser induction of 532 nm wavelength in different levels of energy (2.0 mJ, 2.5 mJ, 3.0 mJ) and pulse number (3, 10, 15). The results show that after laser irradiation of 2.0 mJ, the refractive index of ZnSe increases while the transmittance decreases. Compared with the laser irradiation of 2.5 mJ and 3.0 mJ, the laser irradiation of 2.0 mJ has the most obvious refractive index increase, from 2.489 4 to 2.501 6. The damage threshold of the film also increases from 0.99 J/cm² to 1.39 J/cm² (10-pulse irradiation), and the damage process of the film evolves from zero damage to severe damage and mutation. Besides, the atomic force microscopy (APM) helped test the surface roughness of the preprocessed film, finding a certain drop of the average surface roughness, namely Ra, in the film with laser preprocessing, from 0.563 nm to 0.490 nm (15-pulse laser irradiation).