Effect of structural evolution of ZnO/HfO 2 nanocrystals on Eu 2+ /Eu 3+ emission in glass-ceramic waveguides for photonic applications.

Eu-doped 70SiO2 -23HfO2 -7ZnO (mol%) glass-ceramic waveguides have been fabricated by sol-gel method as a function of heat-treatment temperatures for on-chip blue-light emitting source applications. Structural evolution of spherical ZnO and spherical as well as rod-like HfO2 nanocrystalline structures have been observed with heat-treatments at different temperatures. Initially, in the as-prepared samples at 900 ◦ C, both, Eu2+ as well as Eu3+ ions are found to be present in the ternary matrix. With controlled heat-treatments of up to 1000 ◦ C for 2 h, local environment of Eu-ions become more crystalline in nature and the reduction of Eu3+ to Eu2+ takes place in such ZnO/HfO2 crystalline environments. In these ternary glass-ceramic waveguides, heat-treated at higher temperatures, the blue-light emission characteristic, which is the signature of 4f 6 5d [Formula: see text] 4f 7 energy level transition of Eu2+ ions is found to be greatly enhanced. The as-prepared glass-ceramic waveguides exhibit a propagation loss of 0.4 ± 0.2 dB cm-1 at 632.8 nm. Though the propagation losses increase with the growth of nanocrystals, the added functionalities achieved in the optimally heat-treated Eu-doped 70SiO2 -23HfO2 -7ZnO (mol%) waveguides, make them a viable functional optical material for the fabrication of on-chip blue-light emitting sources for integrated optic applications.