Linear- and nonlinear-optical properties of Eu3+:Y2SiO5 have been investigated. All the energy levels of the7F0,1,2,… ground-state manifold and the 5D0,1,2 excited-state manifold were identified, and they were found to be doubly structured because of the two inequivalent optical sites. Two absorption lines of the 7F0–5D0 transition were studied in detail by using nonlinear spectroscopic techniques, photon-echo and stimulated-photon-echo methods. It was found by the photon-echo measurement that the optical dephasing time for one site is extremely long and is excitation-intensity dependent. With the smallest possible intensity we observed the longest ever dephasing time in a solid, 822 μs, or a 387-Hz homogeneous linewidth. From the stimulated-photon-echo measurement, the linewidth was found to be constant over a wide range of time scales, implying the absence of spectral diffusion in this crystal. These quite advantageous properties of this crystal were used for the demonstration of two novel types of time-domain optical data readout: time- and frequency-domain hybrid optical memory and spectrally programmed coherent transients.
Rare-earth ions doped in crystals with low nuclear-spin densities are highly promising candidates for quantum technology applications. In this study, we investigated the spectroscopic properties of the 7F0 - 5 D0 optical and the hyperfine transitions of Eu3+ ions in a CaWO4 crystal, where the nuclear spin arises solely from the 183W isotope, with a natural abundance of 14%. At a temperature of 3 K, we experimentally identified four distinct crystal field environments for Eu3+ ions in a 0.1 at.% Eu3+ doped CaWO4 crystal. The optical coherence properties of Eu3+ ions in these environments were characterized. Additionally, we resolved the hyperfine structures in the 7F0 ground state and 5D0 excited state, and determined the 7F0 ground state lifetimes using spectral hole-burning techniques. These findings highlight the significant potential of Eu3+:CaWO4 for optical quantum memory applications.
Eu-doped yttrium orthosilicate (Eu(3+) : Y2SiO5) had been a subject being investigated for coherent time-domain optical memory and information processing applications since its ultraslow optical dephasing was discovered several years ago. In this crystal the weakly allowed (7)F0 - (5)D0 transition of europium ions exhibits a sufficient long dephasing time and no spectral difli.usion on a time scale of several hours at low temperature, thus an information pattern or data can be stored as a population grating in the ground state hyperfine levels. On the other hand, the study on photon-echo relaxation shows that the dephasing time T2 of Eu (3+) and other rare-earth ions doped YAG, YAlO3 strongly depends on the intensity of the excitation pulses. In Eu (3+) :YAlO3, an exponential decay of photon-echo with T2 = 53 microseconds if the excitation pulses are weak (5 vJ/pulse) was observed. However, when the excitation pulses are strong (80 pJ/pulse) they observed a much shortened T2 with a highly nonexponential decay pattern. The conclusion they derived is that the intensity-dependent dephasing rate effects are quite general, and it depends on how much the excitation intensity varies. In this paper we use transient grating formation technique showing that a temporal lattice distortion may only occur along crystal c axis, caused by EU (3+) excitation. At high excitation level the produced exciton in conduction band may also couple to the dynamical lattice relaxation process, giving rise to an apparently much shortened dephasing time.
We have employed spectral-hole-burning, coherent-transient, and optical-rf double-resonance techniques to measure various parameters associated with the 580.8-nm
7F0${\mathrm{\ensuremath{-}}}^{5}$
D0 transition of
Eu3+ doped into
Y2O3. In particular, we have measured the hyperfine splittings of the terminal levels (for both
151Eu and
153Eu), an effective thermalization rate of the ground-state
(7F0) hyperfine manifold over the temperature range of \ensuremath{\simeq}4--15 K, and the homogeneous linewidth of the optical transition over the range of \ensuremath{\simeq}14--35 K. Large ratios of inhomogeneous to homogeneous linewidth at elevated temperatures (
103 at 25 K) and long ground-state hyperfine thermalization times (>30 h at 4 K) make this an interesting crystal in the context of spectrally addressable optical memories.
We report the optical study of europium nitrate hexahydrate crystals Eu(NO 3 ) ⋅ 3 6H 2 O and their deuterated version Eu(NO 3 ) ⋅ 3 6D 2 O conducted at 50 mK. The crystals show sub-GHz inhomogeneous linewidths for the F 0 7 ↔ 5 D 0 transition and optical coherence times up to 136 μs for the non-deuterated crystal and 750 μs for the deuterated one. In addition, using the spectral hole burning technique, the hyperfine splittings in the absence of an external field have been estimated for the ground and optical levels. These results suggest that rare-earth nitrate crystals could represent a promising class of materials for quantum information applications as well as for fundamental physics experiments requiring narrow optical transitions and good coherence properties. • Deuterated and non-deuterated europium nitrate crystals were grown using the slow-cooling method. • Optical coherence times up to 0.75 ms were measured at 50 mK using the photon echo technique. • Sub-GHz optical inhomogeneous linewidths were observed. • The hyperfine splittings of the ground and optical states were assessed via spectral hole burning.
Detailed site-selective spectroscopy has been performed as a function of temperature on the ${}^{7}{F}_{0}{\ensuremath{\leftrightarrow}}^{5}{D}_{0}$ transition of
Eu3+:Y2SiO5 for
Eu3+ concentrations of 0.02%, 0.1%, 0.5%, and 1%. Time-domain optical dephasing, spectral hole lifetimes, anisotropic absorption coefficients, inhomogeneous linewidths, and fluorescence lifetimes for
Eu3+ ions at both crystallographic sites were measured. The temperature dependence of the optical dephasing, transition energy, and linewidth of the ${}^{7}{\stackrel{\ensuremath{\rightarrow}}{{F}_{0}}}^{5}{D}_{0}$ absorption was measured and interpreted in terms of Raman scattering of phonons. Photon echo measurements of optical dephasing gave
T2 values as long as 2.6 ms, approaching the limit set by the fluorescence decay time. Spectral hole lifetimes were measured for temperatures from 2 K to 18 K, with observed lifetimes varying from 1 s at 18 K to an estimated value of greater than 20 days at 2 K. Anisotropic absorption coefficients were measured, and an increase in
Eu3+ concentration from 0.02% to 7% produced an increase in the inhomogeneous linewidth ${\ensuremath{\Gamma}}_{\mathrm{inh}}$ from 0.5 GHz to \ensuremath{\sim}150 GHz, indicating that
Eu3+ doping induces significant strain in the crystal. New determinations of many energy levels of
7FJ multiplets have been made for
J=0 to 6.