Amorphous hydrogenated carbon films were formed on the Si (100) wafers by a direct-ion beam deposition method from pure acetylene and acetylene-hydrogen gas mixtures. The films were irradiated with a nanosecond Nd:YAG laser working at the first harmonics (λ1 = 1064 nm), the fourth harmonics (λ4 = 266 nm) or with a Nd:YVO4 laser working at the third harmonic (λ3 = 355 nm). The films were studied by the Raman scattering, micro-Fourier transform infrared and Fourier transform infrared spectroscopies, null-ellipsometry, optical and scanning electron microscope, and Vickers hardness method. Irradiation by the wavelength λ1 = 1064 nm leads to graphitization and formation of the silicon carbide, because of the silicon substrate decomposition. The samples were strongly modified after the irradiation by λ3 = 355 nm - the thickness of the films decreased, and silicon carbide was formed. It was observed that nano-structured materials (e.g. carbon nano-onions, nc-diamond) were formed after the irradiation by λ4 = 266 nm.