Upconversion random lasing in Er3+/Yb3+co-doped germanate-lead-magnesium glass-ceramics

Upconversion Random Laser (UC-RL) based on Yb3+ and Er3+ co-doped germanate-lead-magnesium (GPM) glass-ceramic powder is reported for the first time. Following the glass fabrication by a conventional melt-quenching technique, the samples were devitrified at 815 degrees C for 4 and 8 h, respectively. The samples were grained and excited using an optical parametric oscillator (pulses of 7 ns) tuned at 980 nm, in resonance with the Yb3+ transition F-2(7/2) -> F-2(5/2) and with the Er3+ transition I-4(15/2) -> I-4(11/2.) The input-output curves revealed RL emission at similar to 547 nm for an energy fluence excitation threshold (EFE)(th) of about 0.6 mJ/mm(2) for GPM sample and similar to 0.45 and similar to 0.20 mJ/mm(2) for samples heat-treated for 4 and 8h, respectively. For excitation above the (EFE)(th), a fast pulse in the nanosecond range is observed, corroborating the lasing process. The RL feedback mechanism is due to the light reflections in the particles-air interfaces and to reflections between the glass-crystallites interfaces. Additionally, the Replica Symmetry Breaking (RSB) phenomenon was observed for all samples excited above the (EFE)(th). Pearson correlation coefficients (PCC) maps were also obtained and showed that RL modes were increasingly correlated above (EFE)(th). No reduction of the emission linewidth was observed above (EFE)(th), due to the inhomogeneous broadening that is very large in vitreous matrices. This is the first time that RSB and PCC maps are reported for an UC-RL.