Modulation of photon-echo intensities by electric fields: Pseudo-Stark splittings in alexandrite andYAlO3:Er3+

We describe and demonstrate a method for performing ultrahigh-resolution optical spectroscopy in the time domain which utilizes modulations in the intensity of the two-pulse photon echo in the presence of a perturbation that splits the optical transition frequencies of two or more subgroups of ions. The method is applied to a measurement of the pseudo-Stark effect in alexandrite and ${\mathrm{YAlO}}_3$:${\mathrm{Er}}^{3+}$. Stark shifts of ≃100 kHz are observed, but the technique is capable of resolutions <10 kHz in some systems.