Excitation-induced frequency shift probed by stimulated photon echoes

A stimulated photon-echo study has verified the instantaneous shift ({≤}1 MHz) and subsequent restoration ({~}2 ms) of the transition frequency of an impurity ion in a solid when its neighboring ions are exposed to pulsed optical excitation. Experiments were conducted by monitoring the echo intensity for the ⁷{F}_{0{{-}}}⁵D₀ transition of Eu ions in one site of Y₂{SiO}₅$, while exciting the other site. A photon-echo theory taking account of the stochastic frequency recovery is developed to explain the observations.