Upconversion, avalanche effect and controlled optical switching in Yb3+, Ho3+ co-doped Ca12Al14O33 phosphor

In the present work, Yb3+/Ho3+ co-doped Ca12Al14O33 phosphor has been synthesized and upconversion (UC) fluorescence has been studied by pumping the sample with 976 nm radiation. In addition to a strong UC fluorescence due to Ho3+, an avalanche effect is also observed with an increase in input laser power. At a certain threshold power, optical switching (a switching in emission intensity of different transitions) behavior is observed whose response time has been estimated to be of the order of milliseconds. A substantial heat generation inside the host matrix due to electron-phonon coupling (non-radiative relaxations) of the rare-earth ion and the host matrix has been assigned responsible for the switching phenomenon. The heat generation has been confirmed and estimated using fluorescence intensity ratio (FIR) method. (C) 2012 Elsevier B.V. All rights reserved.