PERSISTENT SPECTRAL HOLE-BURNING OF SOL-GEL-DERIVED EU3-DOPED SIO2 GLASS()

Persistent spectral hole burning (PSHB) was observed at temperatures h igher than 77 K in the sol-gel-derived Eu3+-doped SiO2 glasses. 1Eu(2) O(3) . 99SiO(2) (mole ratio) glass was prepared by heating gel synthes ized from metal alkoxides at 400 to 1000 degrees C. The hole was burne d in the F-7(0)-->D-5(0) line of Eu3+ ions by means of a Rhodamine 6G dye laser at 77 K and the burnt hole depth was measured as a function of temperature. The hole depth increased with increasing OH content in the glass. It was found that the hole burnt at 77 K was thermally fil led and an average thermal barrier height for the hole filling was sim ilar to 0.3 eV, which was higher for the glass heated at high temperat ure, indicating that the stable hole is burned with the increased heat -treatment temperature. It was concluded that the PSHB was formed by t he optically activated rearrangement of proton in the first coordinati ng sphere of the Eu3+ ions.