Photon-echo measurements on the trivalent thulium ion

Photon-echo measurements are reported for the trivalent thulium ion, which differs from all other rare-earth ions in having a single isotope of nuclear spin 1/2. Echo decays on the 3H6(1) ↔ 3H4(1) transition of LaF3+ and YAG+ were magnetic-field dependent at 1.5 K, showing that the dephasing originates from spin fluctuations of nuclei in the host crystals. Coherence times in the range of 7 to 100 μs were measured, corresponding to homogeneous linewidths of tens of kilohertz. The echo decays were nonexponential, providing evidence for spectral diffusion that is due to a distribution of 19F and 27A1 nuclear spin-flip times in the respective hosts. © 1993 Optical Society of America.