Relationship between room temperature hole-burning in glasses and doped Eu-ion concentration

Photochemical hole-burning in sodium-borate glass (35Na 2 O–65B 2 O 3 ) was investigated as a function of doped Eu-ion concentration from 0.1 to 5 mol% both at room temperature and 12 K. In our preparation, 50–70% of Eu 3+ was reduced to Eu 2+ . As the concentration of Eu ion exceeded 1 mol%, the fluorescence was quenched, and meanwhile the photochemical hole started burning. The spectral hole was most efficiently burnt at concentrations between 2 and 3 mol% at room temperature. Low temperature experiment showed that there are three kinds of processes for the hole formation. One is a transient process relaxed within 1–2 min. Another is observed only at low temperatures. The third one is observed persistently even at room temperature. The extent of these components depends on Eu-ion concentration. In view of these concentration dependences, the suggested mechanism of room temperature hole-burning is an energy or electron transfer between Eu 3+ and Eu 2+ . Defect centers created by reduction process of the glass may play a role to help this transfer.