Nanostructure and microripple formation on the surface of sapphire with femtosecond laser pulses

摘要

We have demonstrated the creation of polarization-dependent nanogratings with a period of about 250 nm on the surface of sapphire by scanning the femtosecond laser beam with appropriate irradiation conditions. Laser fluence range for nanograting self-formation was very narrow in the slow scan mode. The grating depth variation was observed with atomic force microscope image analysis. To see the composition distribution in the nanostructure, we carried out the Auger signal analysis. In addition, we found a new periodic structure with a period of a few μm and discussed the complex formation mechanism.