Photon-gated photoconductivity of Pr³⁺:YAG

We have observed photon-gated photoconductivity in Pr, providing clear evidence for photoionization of the trivalent praseodymium ion in the solid state. Photoionization occurs by two-step absorption from 3H4(1) → 1D2(1) followed by an excited-state absorption from 1D2 to the lowest component of the 4f5d configuration. The excitation spectrum of the photocurrent shows sharp 1D2 spectral features, providing unambiguous assignment of the photocurrent. © 1996 Optical Society of America.