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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 o - 5 D o transition of Eu ions in one site of Y 2 SiO 5 , while exciting the other site. A photon-echo theory taking account of the stochastic frequency recovery is developed to explain the observations