Random laser emission from neodymium doped alumina lead-germanate glass powder

Random lasing is reported for the first time, to our knowledge, in neodymium doped alumina lead-germanate (GPA) glass powder. The samples were fabricated by a conventional melt-quenching technique at room temperature, and x-ray diffraction was used to confirm the amorphous structure of the glass. Powders with average grain size of about 2 µm were prepared by grinding the glass samples and using sedimentation in isopropyl alcohol to remove the coarsest particles. The sample was excited using an optical parametric oscillator tuned to 808 nm, in resonance with the neodymium ion (N d ³⁺) transition ⁴ I _9/2→{⁴ F _5/2,² H _9/2}. Random laser (RL) emission at 1060 nm (N d ³⁺ transition: ⁴ F _3/2→⁴ I _11/2) was observed for an energy fluence excitation threshold (E F E ) of about 0.3m J/m m ². Above the E F E , a short RL pulse in the nanosecond range is observed, corroborating the lasing process. Contrary to what one might suppose, the use of large quantities of neodymium oxide (10% wt. of N d ₂ O ₃) in the GPA glass, which leads to luminescence concentration quenching (LCQ), is not a disadvantage, once stimulated emissions (RL emission) occur faster than the nonradiative energy-transfer time among N d ³⁺ ions responsible for the LCQ.