Photon-gated spectral hole burning in Pr³⁺:YAG

We observed photon-gated spectral hole burning in Pr and assigned the hole-burning mechanism to selective photoionization of trivalent praseodymium. Gated holes were observed in absorption lines to the two lowest components of the 1D2 manifold. At 1.4 K the gating ratio is in excess of 1.5 × 104. Strong competition from the transient mechanism of optical pumping of hyperfine levels occurs below 6 K. © 1996 Optical Society of America.