OPTICAL HOLE-BURNING OF EU3-CRYSTALS CAF2( AND PR3+ IN DISORDERED MIXED)LAF3 AND CAF2/YF3/

Spectral hole burning is reported in disordered CaF2 crystals mixed wi th LaF3 and YF3 containing EU(3+) and Pr3+ as probe ions. For Eu3+, ho le burning occurs by population redistribution among the nuclear quadr upole levels while for pr(3+) in the CaF2 with 3, 12, and 30% YF3, per sistent spectral hole burning occurs. A nearly linear temperature depe ndence of the holewidth is observed for both EU(3+) and Pr3+ in these mixed fluorites. The temperature dependence of the holewidth is compar ed with previous results on disordered oxide samples and glasses. The results suggest the presence of a continuous distribution of excitatio ns like those of two-level systems.