Persistent and transient spectral hole burning in Pr3+ - and Eu3+ -doped silicate glasses

Abstract

Persistent and time-resolved transient holes were burnt into the $^{1}\mathrm{D}_{2}$${\ensuremath{\leftarrow}}^{3}$${\mathrm{H}}_{4}$ transition of ${\mathrm{Pr}}^{3+}$ and the $^{5}\mathrm{D}_{0}$${\ensuremath{\leftarrow}}^{7}$${\mathrm{F}}_{0}$ transition of ${\mathrm{Eu}}^{3+}$ in silicate glasses. The holewidths were studied as a function of burning-fluence density, wavelength, and temperature between 0.4 and 12 K. Transient holes arising from optical pumping of ground-state nuclear hyperfine levels were found for both ions at T3 K. Their lifetime decreases with increasing temperature. They are accompanied by symmetrically placed antiholes. For ${\mathrm{Eu}}^{3+}$, two pairs of antiholes were found which are attributed to the two europium isotopes, $^{151}\mathrm{Eu}$ and $^{153}\mathrm{Eu}$. For ${\mathrm{Pr}}^{3+}$, an additional mechanism leading to persistent hole burning dominates above 3 K. The holewidth follows a ${\mathit{T}}^{(1.3\ifmmode\pm\else\textpm\fi{}0.1)}$ dependence for ${\mathrm{Pr}}^{3+}$ and a ${\mathit{T}}^{(1.0\ifmmode\pm\else\textpm\fi{}0.1)}$ dependence for ${\mathrm{Eu}}^{3+}$. The temperature dependence is the same as that of the contribution of the two-level systems to the specific heat measured on the same samples and in the same temperature range. The quadrupole splittings of the $^{7}\mathrm{F}_{0}$ ground state and the crystal-field splittings of the $^{7}\mathrm{F}_{1}$ and $^{7}\mathrm{F}_{2}$ levels of ${\mathrm{Eu}}^{3+}$ as a function of excitation wavelength indicate that the strength of the noncubic component of the crystal field varies monotonically for excitation across the $^{5}\mathrm{D}_{0}$${\ensuremath{\leftarrow}}^{7}$${\mathrm{F}}_{0}$ absorption band, falling to zero at the long-wavelength edge. The hole width shows a similar variation with excitation frequency. No influence of the experimental time scale on the hole width was detected for either sample between ${10}^{\mathrm{\ensuremath{-}}2}$ and ${10}^{2}$ s.