Abstract
The hyperfine structure of the D21 3 H4 transition of Pr3+: yttrium aluminum garnet (YAG) is studied using a photon echo modulation technique. The Fourier transform of modulation data gives hyperfine frequencies of the D21 state as 3.42 and 5.96 MHz. The photon echo modulation is a very sensitive function of the atomic environment, and we find that the site symmetry of Pr3+ impurity ions in YAG is lowered to C2 from the D2 symmetry of Y3+ ions.