Optically generated pseudo-Stark effect in ruby

We report observations of an optically produced splitting of the luminescence lines of concentrated ruby samples for optical intensities of approximately 200 W/${\mathrm{cm}}^2$. This splitting is attributed to optical generation of a large, uniform electric field (${10}^6$ V/cm). At high intensities ($l>\mathrm{}2\mathrm{}$ kW/${\mathrm{cm}}^2$) high photoconductivity causes the splitting to decrease and disappear. It is suggested that the field-generation mechanism is directional charge transfer via two-step excitation of ${\mathrm{Cr}}^{3+}$ ion or ion clusters. The required electrical asymmetry is shown to be due to a growth-induced anisotropy of the ${\mathrm{Cr}}^{3+}$ ion distribution.