Research Of The Properties Of Diamond-like Carbon Films Processed By High Power Lasers

Diamond-like carbon (DLC) films can be applied in rugged environment such as sandstorm and salt fog owing to their excellent properties, but their low laser-induced damage threshold (LIDT) constrains the applications in the infrared high power laser systems, laser confrontation and fence systems. Taking appropriate laser pre-irradiating methods can change the microstructures of DLC films, as a result of this, affected the laser damage characteristics of the films.Hydrogen-free and hydrogenated diamond-like carbon (a-C:H) films were deposited by unbalanced magnetron sputtering method. Microstructure and properties of the films were detected in order to research changes of them before and after the laser irradiation. Hydrogen-free DLC films were irradiated by a laser energy which is very close to the LIDT. The optical properties, surface morphology and the microstructure of films before and after irradiation were tested and analyzed. The laser with energy of less than 60% of LIDT was applied to irradiate the a-C:H films, and the surface roughness and LIDT of the films were investigated. The results are as follows.(1) As for hydrogen-free DLC films, when laser beam energy fluencies close to LIDT, with the increase of the laser energy density, the extinction coefficient increases, the transmittance, refractive index and LIDT decrease. The results of the Raman spectrum shows that the sp3 bonding transforms into sp2 and the DLC films are graphitized. With the increase of the laser fluencies, the graphitization degree gets deeply.(2) By using a laser with energy close to LIDT to irradiate the hydrogenated-free DLC films, the cluster shapes in the films surface become irregularly, and their sizes become larger, the distribution uniformity in substrates reduces, and the surface are scraggy. The more irregular clusters, greater size, poorer distribution uniformity, and the scraggier surface can be obtained at the higher laser fluencies.(3) For hydrogenated DLC film, the irradiation energy is 20%,40% and 60% of LIDT, all of them do not influence the transmittance, the first two have no effect in roughness of the LIDT, when the fluencies increased to 60% of LIDT, the roughness is reduced and LIDT is improved.