Persistent spectral hole burning of sol-gel-derived Eu3+-doped SiO2 glass

Persistent spectral hole burning (PSHB) was observed at temperatures higher 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 synthesized from metal alkoxides at 400 to 1000 degrees C. The hole was burned 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 filled and an average thermal barrier height for the hole filling was similar to 0.3 eV, which was higher for the glass heated at high temperature, indicating that the stable hole is burned with the increased heat-treatment temperature. It was concluded that the PSHB was formed by the optically activated rearrangement of proton in the first coordinating sphere of the Eu3+ ions.