We report what is to our knowledge the first measurement of linear and nonlinear spectroscopic properties for the (7)F(0)-(5)D(0) transition of Eu(3+):Y(2)SiO(5). Two clearly resolved lines at 579.879 and 580.049 nm, stemming from different sites, show dissimilar photoluminescence and hole spectra. In addition, these two sites have different inhomogeneous and homogeneous linewidths, which suggests that the local-field effect is smaller for one site. Specifically, the less affected site exhibits the longest dephasing time (822 micros) of any solid, which corresponds to a homogeneous linewidth of 387 Hz, and this linewidth is found to persist for hours without apparent spectral diffusion.
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.
We report a spectroscopic study of the 7F0–5D1 transition of europium ions in crystal yttrium orthosilicate (Eu3+:Y2SiO5) with a focus on low-temperature properties relevant to its use in time-domain optical data storage. The optical dephasing time T2 for this green transition was found to be approximately 50 μs for Eu3+ in one optical site (site 1) and 56 μs for Eu3+ in the other site (site 2), both of which exceeded their respective excited-state lifetimes (32 μs for site 1 and 42 μs for site 2). Of the two optical sites, the transition on site 2 has a slightly larger inhomogeneous linewidth (~2.7 GHz) but a significantly larger oscillator strength (~6 × 10−8), making it a good candidate for time-domain optical storage. The hyperfine structures of the transition for both sites were also measured by spectral hole burning.
We have measured the optical dephasing time of Er(3+) transitions near 1.5 microm in the two crystallographically inequivalent sites of Y(2)SiO(5), using an external-cavity diode laser amplified by an erbium-doped fiber amplifier. Two-pulse photon echoes were observed at zero field and in magnetic fields up to 55kG, with dephasing times as long as 580 micros (corresponding to a linewidth of 550 Hz). Stimulated echoes were also measured and showed evidence of spectral diffusion during the 13-ms lifetime of the (4)I(13/2) level.
Optical hole burning is used to study optical dephasing of the 7F0 ⇒ 5D0 transition in samples of Y2O3:Eu3+ grown by both flame fusion and laser-heated pedestal growth. The samples exhibited a wide variation in their low-temperature hole widths, and the measured hole linewidths were in reasonable agreement with homogeneous linewidths obtained from values of T2 that were determined with two-pulse photon echoes. The sample that had the longest value of T2 (510 μs) from the echo measurements gave a hole width of 3.5 kHz. This is believed to be the narrowest spectral feature observed directly in the frequency domain for a solid. Other samples produced wider holes that were not correlated with the Eu3+ impurity concentrations. Time-resolved hole burning in one of the samples showed a slow and continuous broadening of the spectral hole from 130 kHz at 3 ms to 900 kHz at 10 s after hole burning. It is suggested that the additional broadening is associated with some form of disorder modes in this ordered crystalline solid.
The optical spectroscopy and dynamics of three materials; Eu^3+:Y2SiO5, Pr^3+:Y2SiO5, and Tm^3+:Y2SiO5 that are of interest for application in persistent spectral holeburning optical memory and signal processing devices were investigated using linear and nonlinear spectroscopic techniques.Two-pulse photon echoes have been used to measure the homogeneous linewidths.The effects of instantaneous spectral diffusion were systematically studied to allow accurate determination of the optical resonance widths, and external magnetic fields were applied to characterize the effects of fluctuating nuclear spins of the host lattice on dephasing of the dopant ion.The 7F0 → 5D0 transition of 0.1% Eu^3+ in the two crystallographic sites of Y2SiO5 was studied using photon echoes.Using this material, we succeeded in measuring the narrowest optical resonance in a solid by shielding the crystal from stray electromagnetic fields and using sufficiently low laser power to minimize contributions from instantaneous diffusion.The homogeneous linewidths measured in a magnetic field of 100 G are 122 Hz (site 1) and 167 Hz (site 2).These widths are dominated by population decay, but up to 20 Hz is attributed to 89Y spin fluctuations which have been reduced by the applied magnetic field.Similar studies were performed to determine the contributions to the homogeneous linewidth of the 3H4(1) → 1D2(1) transition for both sites of 0.02% Pr^3+ in Y2SiO5.Linewidths of 2.1 kHz (site 1) and 0.85 kHz (site 2) were obtained with an applied magnetic field of 77 G.A significant contribution of 89Y nuclear spin fluctuations to the zero-field homogeneous linewidth was found.Optically detected nuclear magnetic resonance measurements determined the hyperfine structure of the 3H4 ground state for each site, and photon echo nuclear double resonance was used to determine the hyperfine levels of the lowest component of the 1D2 manifold. 3) 2.1? Ec,2S
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.