Electrons in Stark Sublevels of Rare-Earth Ions

Renata Reisfeld

Andrei V. Ivanov, Yu. Rozhdestvensky, E. Yu. Perlin

A mechanism for laser cooling of crystals doped with rare-earth ions is proposed. The mechanism involves two-photon Raman scattering through the dipole-allowed 5d ion level, electron–phonon transitions between the Stark-split sublevels, and fluorescence from the excited ion level. It is shown that, under the conditions of coherent pumping, the total population of the ground level is transferred to the excited level of the rare-earth ion, thus increasing the cooling power and accelerating the cooling process. The involvement of dipole-allowed transitions yields an increase in the cooling efficiency by 14% compared to the efficiency of direct pumping at transitions between the 4f levels. Estimations show that the temperature of the sample cooled by the proposed mechanism can reach 82.9 K for current materials with a background absorption coefficient of 4.0×10−4 cm−1.

A. Taroni

USM ADMIN

Effects of the electron-phonon interaction for rare earth ions (RE) in crystals are multi-phonon relaxation, vibronic bands, band broadening depending on temperature or non-resonant energy transfer assisted by phonons. Since the Stark splitting for RE ions are of the order of lattice phonon energy, it could arise and other related effects, especially in the approximation of quasi-resonant processes. If the distance between two Stark levels is close to the region of resonance phonon spectrum, then electron-phonon interaction creates mixed vibronic states, which causes changes in the optical spectral lines (widening, asymmetry, splitting or displacement). The modeling of interaction of the electron-phonon resonance for RE ion Yb3+ in three different laser crystals is the purpose of this paper. Keywords: electron-phonon interaction, rare earth ions, adaptive application.

Jörg Wrachtrup

Erhan Sağlamyürek, Thomas Lutz, Lucile Veissier +4 more

Long-lived population storage in optically pumped levels of rare-earth ions doped into solids, referred to as persistent spectral hole burning, is of significant fundamental and technological interest. However, the demonstration of deep and persistent holes in rare-earth ion doped amorphous hosts, e.g., glasses, has remained an open challenge for many decades---a fact that motivates our work towards a better understanding of the interaction between impurities and vibrational modes in glasses. Here we report the observation and detailed characterization of such holes in an erbium-doped silica glass fiber cooled to below 1 K. We demonstrate population storage in electronic Zeeman sublevels of the erbium ground state with lifetimes up to 30 seconds and 80% spin polarization. In addition to its fundamental aspect, our investigation reveals a potential technological application of rare-earth ion doped amorphous materials, including at telecommunication wavelength.