We have studied the processes of photocoloration and discoloration in and relevant crystals. We show the following: (1) The coloration rate in does not depend on Mn concentration. (2) The effective recombination time of free electrons with ions and deep traps is of the order of ms. (3) The rate of photocoloration increases with an increase in temperature. (4) The discoloration kinetics in are strongly nonexponential. At room temperature the effective discoloration time approximates 120 years. (5) At increased temperatures the discoloration kinetics accelerate dramatically. (6) We have grown and characterized and crystals. The activation energy in these crystals is much larger than that in This suggests the great potential of and in terms of permanent data storage.
© 2001 Optical Society of America