Frequency upconversion involving triads and quartets of ions in a Pr3+/Nd3+ codoped fluoroindate glass

Abstract

Frequency upconversion (UC) processes involving energy transfer (ET) among Nd3+ and Pr3+ ions in a fluoroindate glass are reported. In a first experiment, the excitation of Pr3+ [transition H34→D32] and of Nd3+ [transition I49/2→(G27/2+G45/2)] was achieved with a dye laser operating in the 575–590 nm range. In a second experiment, the Nd3+ ions were excited with the second harmonic of a Nd: YAG laser at 532 nm. The ET processes leading to UC in both experiments were studied by monitoring the blue fluorescence decay at 480 nm due to the transition P30→H34 in Pr3+. In the more relevant UC process, quartets of ions (Nd–Nd–Pr–Pr) are excited due to absorption of three laser photons by two Nd3+ ions which transfer their energy to two Pr3+ ions. Each Pr3+ ion promoted to the P30 level decays to the ground state emitting one photon in the blue region. This conclusion was achieved investigating the dependence of the UC fluorescence intensity as a function of laser intensity, samples concentrations, and temporal behavior of the UC signal. Other UC processes involving nonisoionic groups of three ions are also reported.