Stimulated-photon-echo spectroscopy. I. Spectral diffusion inEu3+:YAlO3

Abstract

Systematic measurements of stimulated-photon-echo intensities as a function of the first-to-second (τ) and second-to-third (T) pulse separations allow the investigation of the dynamical properties of the spectral diffusion for the ${}_{}{}^7{}_{}{}^{}$ ${\mathit{F}}_0$ ${\mathrm{-}}^5$ ${\mathit{D}}_0$ transition of a cryogenic ${\mathrm{Eu}}^{3+}$:${\mathrm{YAlO}}_3$ sample. The existence of spectral diffusion was verified by the significant broadening (from 1.2 to 7.2 kHz) of the homogeneous linewidth (Γ) as T increases from microseconds to milliseconds, the effect being attributed to the flip flop of nearby aluminum nuclear spins surrounding the ${\mathrm{Eu}}^{3+}$ ion. A similar broadening effect (from 0.61 kHz, to a few kHz) was also observed in the presence of a static magnetic field ${\mathit{H}}_0$=137 G, but with a much slower diffusion rate. To explain these observations, we use three theoretical models: the Bai-Fayer model, the diffusion-equation model, and the Monte Carlo model. Each agrees reasonably well with the experimental data and indicates the flip rates of sub-kHz order at ${\mathit{H}}_0$=0 and an order of magnitude lower at 137 G.