Room-temperature persistent spectral hole burning of Eu3+-doped sodium borate glasses

Persistent spectral hole burning has been observed at room temperature for Eu3+ incorporated in sodium borate glasses prepared under reducing conditions. The measurements at 77 K indicate that the relative hole area increases with increasing the molar ratio of Eu2+ to Eu3+ when the content of Eu2+ is low, whereas the relative hole is almost independent of the molar fraction of Eu2+ when the content of Eu2+ is high. We suggest that photoinduced reduction of Eu3+ is responsible for the room-temperature hole burning of Eu3+ in the present sodium borate glasses and that the predominant center which captures a positive hole formed by the reduction of Eu3+ is the coexisting EU2+. (C) 2000 Published by Elsevier Science B.V. All rights reserved.