Random laser in Nd:YBO3 nanocrystalline powders presenting luminescence concentration quenching

Enhancement of the random laser (RL) performance in crystalline nanopowders of vaterite-type orthoborate NdxY1.000-xBO3 (0.015 <= x <= 0.040) was investigated by exciting the trivalent neodymium ions (Nd3+) at 806 nm in resonance with the ground state transitions I-4(9/2) -> {F-4(5/2), H-2(9/2)}. RL emission at 1056 nm, due to the Nd3+ transition F-4(3/2 )-> I-4(11/2), was observed and characterized. Although luminescence concentration quenching was detected for x > 0.007, an improvement of the RL performance was demonstrated for large Nd3+ concentrations. This feature was understood considering that the RL onset time is shorter than the nonradiative relaxation time of the F-4(3/2) emitting state. The experimental results are supported by numerical simulations based on coupled rate-equations for the excited ions density and the number of photons participating in the random lasing process. The present results can motivate further RL studies with large concentration of trivalent rare-earth ions in glassy, ceramics, and crystalline matrices, which are normally avoided due to the concentration quenching.