Photon avalanche in Pr3+: LaCl3

The phenomenon of photon avalanche has been studied in Pr3+:LaCl3 with a do pant concentration of 8%. In our experiments, a tunable dye laser is resona nt with one of the H-3(5) --> P-3(0) excited state transitions in the range of 545-550 nm, and the fluorescence from the P-3(J) states is monitored. U nder the appropriate circumstances, the fluorescence output as a function o f incident laser power is nonlinear above a critical threshold value. This effect is due to an efficient cross relaxation between neighboring Pr ions that results in a nonlinear build up of the H-3(5) population leading to a dramatic increase in the absorption of the laser light and in the fluoresce nce from the P-3(J) levels under continuous wave excitation. In this paper, we will report on the steady-state spectra, temporal evolution near the th reshold, and the laser power dependence of the avalanche signal as a functi on of temperature (80 K to room temperature). (C) 1999 Elsevier Science B.V . All rights reserved.