부산대학교 도서관

Abstract: The formation of self-organized subwavelength ripples on Al, Si, CaF2 and CR-39 induced by 25fs laser pulses at central wavelength of 800nm has been observed under certain experimental conditions. In case of Al subwavelength gratings with periodicities ranging from 20 to 220nm are reported. For CaF2 the periodicity goes up to 625nm. In case of Si, nano-gratings have the periodicity of 10–100nm. The interspacing of these gratings is 60nm in case of CR-39. These features which are significantly shorter than incident laser wavelength are observed at the irradiation fluence slightly higher than the ablation threshold regardless of the target material. In addition to these nanoripples, classical or microripples with an average spacing of 1–2μm have also been registered on irradiated surfaces of Al and Si. These microripples have appeared at fluence higher than that is required for nanoripple-formation. It has been found that the formation of the laser-induced ripples is strongly dependent and quite sensitive to the incident laser fluence and the selection of material. [Copyright &y& Elsevier]