Studies of the red anti-stokes emission of erbium ions in the Y2O2S: Er,Yb phosphor system

Excitation of the anti-Stokes red emission radiation from erbium ions by 1000 nm radiation in the Y₂O₂S: Er, Yb system has been investigated using a range of samples with widely varying erbium but fixed ytterbium content. A square law intensity dependence is found favouring the models of Sommerdijk and of Hewes and Sarver. Comparison of Stokes and anti-Stokes excitations of both green and red erbium emissions then eliminates the Hewes and Sarver model. Studies using twin-beam excitation as by Kuroda et al. (1000 nm plus 1500 nm) and over a range of temperatures give evidence that the previous assumption of the non-radiative, multiphonon relaxation between the ⁴I_{$\text{11}\text{2}$} and ⁴I_{$\text{13}\text{2}$} states following the first 1000 nm excitation is not satisfactory and suggest that this transition is radiative (2500 nm radiation).