Spectroscopy and multiwave mixing inPr3+:LaF3

Photon-echo and stimulated-photon-echo experiments in ${\mathrm{Pr}}^{3+}$:${\mathrm{LaF}}_3$ on the three transitions, ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$-${(}^3$ ${\mathrm{H}}_5$ ${)}_1$, ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$-${(}^3$ ${\mathrm{H}}_5$ ${)}_2$, and ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$-${(}^3$ ${\mathrm{H}}_6$ ${)}_1$ [none of which, therefore, involves the ${(}^3$ ${\mathrm{H}}_4$ ${)}_1$ ground state] at liquid-He temperatures have revealed the presence of anomalously large residual homogeneous linewidths. The subscripts (e.g., 1,2) denote the crystal-field-split levels of the ${\mathrm{Pr}}^{3+}$ ion states. Amplitude-modulated trilevel echoes were observed involving the ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$-${(}^3$ ${\mathrm{H}}_5$ ${)}_1$ and ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$-${(}^3$ ${\mathrm{H}}_5$ ${)}_2$ transitions while no trilevel echoes were observed involving the ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$-${(}^3$ ${\mathrm{H}}_4$ ${)}_1$ and ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$-${(}^3$ ${\mathrm{H}}_6$ ${)}_1$ transitions. Photon echoes were observed on many of the satellite lines of the principal resonance ${}_{}{}^3{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$-${(}^3$ ${\mathrm{H}}_4$ ${)}_1$ transitions.