Up-conversion emission in violet from yellow in Nd3+: SiO2–TiO2–Al2O3 sol-gel glasses

This paper reports an up-conversion emission in violet (408 nm) from Nd3+-doped 93SiO2:7TiO2:20AlO1.5 glasses synthesized by the sol-gel process. Upon excitation at 583 nm (4I9/2→4G5/2), a bright violet up-conversion emission at 408 nm has been observed. The behavior of the up-conversion luminescence has been compared with that of the normal luminescence at both 408 and 1064 nm. The results show that while no concentration quenching for up to 2 mole Nd content is observed for the up-conversion emission, such an effect can be observed for the normal luminescence cases. Although the up-conversion luminescence has a shorter lifetime and weaker intensity, it is of use to the development of sol-gel glass-based waveguide lasers operating at the violet wavelength.