No abstract

We investigated the random lasing process and Replica Symmetry Breaking (RSB) phenomenon in neodymium ions (Nd3+) doped lead-germanate glass–ceramics (GCs) containing MgO. Glass samples were fabricated by conventional melt-quenching technique and the GCs were obtained by carefully devitrifying the parent glasses at 830 °C for different time intervals. The partial crystallization of the parent glasses was verified by X-ray diffraction. Photoluminescence (PL) enhancement of $$\approx$$ ≈ 500% relative to the parent glasses was observed for samples with a higher crystallinity degree (annealed during 5 h). Powders with grains having average size of 2 µm were prepared by griding the GCs samples. The Random Laser (RL) was excited at 808 nm, in resonance with the Nd3+ transition 4I9/2 → {4F5/2, 2H9/2}, and emitted at 1068 nm (transition 4F3/2 → 4I11/2). The RL performance was clearly enhanced for the sample with the highest crystallinity degree whose energy fluence excitation threshold (EFEth) was 0.25 mJ/mm2. The enhanced performance is attributed to the residence-time growth of photons inside the sample and the higher quantum efficiency of Nd3+ incorporated within the microcrystals, where radiative losses are reduced. Moreover, the phenomenon of Replica Symmetry Breaking (RSB), characteristic of a photonic-phase-transition, was detected by measuring the intensity fluctuations of the RL emission. The Parisi overlap parameter was determined for all samples, for excitation below and above the EFEth. This is the first time, for the best of the authors knowledge, that RL emission and RSB are reported for a glass–ceramic system.

Random Lasing is reported for the first time in Nd3+-doped lead-germanate glass powders. Above laser threshold (0.3 mJ/mm2) a short pulse, in the nanosecond range is observed corroborating the lasing process.

Photoluminescence to amplified spontaneous emission transition is observed for the first time in a Nd3+ doped zinc tellurite (TZO) glass powder. The results indicate TZO glasses are promising scattering gain medium for random lasing.

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 r m t h ) of about 0.3 m J / m m 2 . Above the E F E t h , 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.