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.