Persistent spectral hole burning of sol-gel-derivedEu3+−dopedSiO2glass

Persistent spectral hole burning (PSHB) was observed at temperatures higher than 77 K in the sol-gel-derived ${\mathrm{Eu}}^{3+}-$doped ${\mathrm{SiO}}_2$ glasses. ${1\mathrm{E}\mathrm{u}}_2{\mathrm{O}}_3{\mathrm{\cdot }99\mathrm{S}\mathrm{i}\mathrm{O}}_2$ (mole ratio) glass was prepared by heating gel synthesized from metal alkoxides at 400 to 1000 °C. The hole was burned in the ${}^7{F}_0{\to }^5{D}_0$ line of ${\mathrm{Eu}}^{3+}$ 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 ∼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 ${\mathrm{Eu}}^{3+}$ ions.