Femtosecond laser direct writing of TiO2 crystalline patterns in glass

Crystalline TiO2 was induced three dimensionally inside a glass sample by 800-nm, 250-kHz femtosecond laser irradiation. Micro-Raman spectra and X-ray diffraction analysis indicated that the laser-induced crystals were monophase TiO2 rutile. A periodic structure consisting of TiO2 rutile crystalline lines was inscribed in the glass sample by continuously moving the focal point of the laser beam. This technique may be useful for fabricating integrated optical devices in glasses.