Space-selective growth of frequency-conversion crystals in glasses with ultrashort infrared laser pulses

We report on space-selective growth of a second-harmonic-generation β‐BaB2O4 (BBO) crystal inside a BaO–Al2O3–B2O3 glass sample at the focal point of an 800-nm femtosecond laser beam. A spherical heated region was formed during the focused laser irradiation through observation with an optical microscope. We moved the heated region by changing the position of the focal point of the laser beam relative to the glass sample. We grew BBO crystal continuously in the glass sample by adjusting the moving speed of the heated zone. Our results demonstrate that functional crystals can be formed three dimensionally in glasses by use of a nonresonant ultrashort pulsed laser.