NEW TRANSPARENT NONLINEAR-OPTICAL TELLURITE-BASED GLASS-CERAMICS

New transparent tellurite-based glass-ceramics in which the crystallin e phase with a particle size of 10-20 nm has a face-centered cubic str ucture have been prepared in the system K2O-Nb2O5-TeO2. The cubic phas e is formed by annealing of original glasses around 390 degrees C and transforms into another stable phase at temperatures above 450 degrees C. Second harmonic generation (SHG) is clearly observed in the transp arent glass-ceramics containing the cubic crystalline phase, with the second harmonic intensity comparable to that in electrically poled TeO 2-based glasses. A very small distortion of the cubic structure might be present, resulting in SHG. Transparent glass-ceramics containing th e cubic crystalline phase have also been fabricated in the system of L i2O or Na2O-Nb2O5-TeO2, but shoved no SHG. Since glass-ceramics have v arious advantages for materials design, e.g., long fibers or desired s hapes, in comparison with single crystals and sintered ceramics, devel opment of transparent glass-ceramics showing SHG would give a large im pact in the field of nonlinear optical materials.