Green emission from Cr, Dy co-doped sol–gel SiO2 glasses

Silica glasses singly doped and co-doped with Cr ions and Dy ions have been prepared by sol–gel method and their photoluminescence (PL) properties have been studied. The emission spectrum of Dy singly doped sample shows a band around 450 nm with a shoulder band around 480 nm, Cr singly doped sample consists of three bands around 450, 530 and 620 nm, and Cr, Dy co-doped samples show two bands around 450 and 530 nm. The relative PL intensity of the green emission at 530 nm in co-doped samples increases greatly compared with the singly doped. These two bands at 450 and 530 nm are respectively assigned to the defects in silica network and a complex luminescence centers associated with Cr ions. The quenching effect of metal ions and energy transfer process could be responsible for the change of PL properties in the co-doped samples.