Phase transformation and nanograting structure on TiO₂ rutile single crystal induced by infrared femtosecond laser

In this paper, Titanium dioxide (TiO_2) rutile single crystal was irradiated by infrared femtosecond laser pulses with repetition rate of 250 kHz. For a P-polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was formed . The periodicity is much less than the laser wavelength. The direction of nanograting alignment depends on the polarization laser beam. Micro-Raman spectra show that the intensity of E_g Raman vibrating mode of rutile phase increases and that of A_1g Raman vibrating mode decreases apparently within the ablation crater. With the increase of irradiation time and laser average power, the Raman vibrating modes of anatase phase emerged. Rutile phase of TiO_2 single crystal is partly transformed into anatase phase.