A theoretical description of the temperature-dependent dephasing rate of rare-earth ions in glass is given for temperatures
T<1 K. The model invokes elastic dipole-dipole interactions between the rare-earth ions and atomic tunneling systems. The calculation explains features of a recent photon-echo experiment on Si
O2:
Nd3+, namely, the magnitude and
T1.3 dependence of the dephasing rate.
Optical dephasing of paramagnetic ions and molecules in organic and inorganic amorphous solids at low temperatures (≲100K) is characterized by unusual temperature dependences and enhanced relaxation rates compared to crystalline systems1. For a large variety of impurity-host combinations the dephasing rate has been found to follow a Tm temperature dependence with m approximately 2. Several theories have attempted to explain this behavior by assuming interactions between the optical center, phonons, and atomic tunneling systems. However, the role of the intrinsic disorder in optical dephasing in these systems is not clearly understood.
Optical dephasing of Pr3+ and Tm3+ ions doped in transparent oxyfluoride glass ceramics was studied with the two-pulse photon echo technique. It was found that the dephasing time of rare earth ions is dramatically less in nanocrystals embedded in a glass matrix than in bulk crystals. A quasi-linear temperature dependence obtained at low temperatures proved that the long-range interaction of the ions inside the nanocrystals with the two level systems of the glass matrix dominates the optical dephasing. The local thermal effect in glass ceramics containing nanocrystals elevates the local temperature, which results in the reduction of optical dephasing time. For Tm(3+)-doped glass ceramics, the elevation of local temperature induced by the irradiation of excitation laser even quenched the photon echo signals in the experimental study.