Periodical Surface Nanostructures Induced by Femtosecond Laser

Laser Induced Periodical Surface Structures – LIPSS, commonly known as ripples, obtained in metals under femtosecond laser irradiation have been extensively investigated by many research groups. Depending on the irradiation... [ view full abstract ]

Laser Induced Periodical Surface Structures – LIPSS, commonly known as ripples, obtained in metals under femtosecond laser irradiation have been extensively investigated by many research groups. Depending on the irradiation conditions, such as laser fluence, number of laser pulses or laser wavelength, different morphology and ripples periods has been obtained: Low Spatial Frequency LIPSS (LSFL) with a periodicity close to the incident laser wavelength, λ, with orientation perpendicular to the laser polarization, and High Spatial Frequency LIPSS (HSFL) with a periodicity from λ/2 up to λ/10, with orientation parallel to the laser polarization. Such micro- and nano-textured surfaces have important applications such as fabrication of bio-mimetic substrates for cells growth and proliferation, surfaces with modified tribologic or wetting properties, security marking.
Our previous experimental observations are complemented by calculations based on the classical interference theory, surface plasmon and surface harmonics generation theories. However, the mathematical model for surface harmonics generation involved in ripples formation doesn't provide reliable predictions and requires further investigations. In order to achieve this, using a large interval of wavelengths for the incident radiation provides a significant advantage. Our latest experiments are emphasized on finding whether there is a correlation between HSFL produced with wavelengths in the NIR region of the spectrum, and LSFL produced with UV radiation. Experimental results and the formation mechanisms of ripples structures are discussed.