Photosensitivity and optical performance of hydrogenated amorphous carbon films processed by picosecond laser beams

In this work we investigate the photosensitivity of hydrogenated amorphous Carbon films (a-C:H) and the changes in their structural features and optical properties, when they are exposed to picosecond laser beams of various wavelengths (Nd:YAG, 1st harmonic, λ = 1064 nm and 4th harmonic, λ = 266 nm). The different light-matter interactions, which take place for the various laser wavelengths, are considered and discussed. The main findings include the formation of SiC at the a-C:H film/Si interface and the film graphitization, when the 1064 nm and 266 nm beams, respectively, are used. Finally we managed to vary locally the refractive index in the range of 1.60-1.95 (20% variations) by laser processing, a fact that is very important for various applications in photonics.