Space-selective precipitation of non-linear optical crystals inside silicate glasses using near-infrared femtosecond laser

Tightly focused laser pulses with approximately 120 fs duration and with a wavelength of 800 nm have been used to induce space-selective precipitation of crystals with large second-order non-linear optical susceptibilities for BaO–TiO2–SiO2, Na2O–BaO–TiO2–SiO2, and Li2O–Nb2O5–SiO2 glass systems. During the laser irradiation, blue light due to the second harmonic generation is observed at 400 nm in response to the precipitation of the crystals in the vicinity of the focal point of the laser beam. X-ray diffraction analysis indicates that only a single phase of LiNbO3 is observed for Li2O–Nb2O5–SiO2 glass system, while BaTiO3 and Ba2TiSi2O8 phases are precipitated for Na2O–BaO–TiO2–SiO2 and BaO–TiO2–SiO2 glass systems. The elemental analysis around the irradiated area using an electron probe microanalyzer reveals that the laser irradiation allows glass-constituting cations to migrate to bring about the precipitation of a ring-shaped crystalline phase.