PERSISTENT INFRARED SPECTRAL HOLE BURNING OF TB3+ IN THE GLASSLIKE MIXED-CRYSTAL BA1-X-YLAXTBYF2+X+Y

Persistent IR spectral holes that exhibit glasslike characteristics-highly nonexponential low-temperature relaxation behavior and a broad distribution of barrier heights observable in thermal-cycling studies-have been produced in the inhomogeneously broadened 4.5-mu-m F-7(6) --> F-7(5) electronic absorption band of the Tb3+ ion in the mixed crystal Ba1-x-yLaxTbyF2+x+y. Investigations of six compositions, ranging from x = 0, y = 0.005 to x = 0.30, y = 0.05, reveal no hole burning for the x = 0, y = 0.005 case and a hole-burning quantum efficiency of the order of 5 x 10(-7) with a weak dependence of the lanthanide fraction for x + y greater-than-or-less-than 0.05. For all compositions with x + y greater-than-or-equal-to 0.05 hole behavior is virtually identical, with both the widths and the peak positions of the distributions of relaxation rates and barrier heights for these mixed crystals being typical of those found for glasses.