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/cm². This splitting is attributed to optical generation of a large, uniform electric field (10⁶ V/cm). At high intensities ($l>2$ kW/cm²) 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 Cr³⁺ ion or ion clusters. The required electrical asymmetry is shown to be due to a growth-induced anisotropy of the Cr³⁺ ion distribution.