Crystallization of langasite-type phases in gallium germanate glasses and optical properties of crystallized glasses

Langasite-type crystals such as Ba3Ga2Ge4O14 and BaGa4La2Ge2O14 are formed through the crystallization of gallium germanate glasses with stoichiometric compositions corresponding to langasite-type phases and optical properties of crystallized glasses are clarified. It is found that the single langasite-type phase is easily formed in each corresponding glass. The crystallized glasses with highly oriented langasite-type crystals at the surface are fabricated using an ultrasonic surface treatment method. The crystallized glasses with BaxGa5−xLa3−xGe1+xO14 phases show moderate second harmonic (SH) intensities of 5-75 times as large as α-quartz, and it is found that the SH intensity of BaxGa5−xLa3−xGe1+xO14 phases increases with the increase of the La3+/Ba2+ ratio. The feature of fluorescence spectra of Eu3+ ions incorporated into langasite-type crystals is also discussed.