Periodic microstructures produced by femtosecond laser irradiation on titanium plate

The periodic microstructures on titanium plate were formed by the irradiation of the femtosecond laser with the laser wavelength of 800 nm and the pulse length of 100 fs. They were oriented to the direction parallel to the laser polarization vector and their (parallel periodic microstructures) period was 1.5-2.4 μm. The periodic nanostructures were also produced by the femtosecond laser ablation, which were oriented to the direction perpendicular to the laser polarization vector and whose period was about 700 nm. Our results indicated that the laser fluence required for the parallel periodic microstructures was higher than that for the periodic nanostructures. The parallel periodic microstructures and the periodic nanostructures might be formed by an intensity modulation, which arose from the interaction of the laser and its scattered wave with a surface wave. The number of laser pulses to irradiate Ti plate was increased from 10 to 110. From 50 pulses, microdots were generated on the hills of the parallel periodic microstructures. From 70 pulses, the parallel periodic microstructures were varied to those with spatial modulation on the hills and the period of them was increased due to the bonding of the hills.