Photon-gated hole burning: A new mechanism using two-step photoionization

We have observed photon-gated spectral hole burning, i.e., hole burning that occurs only in the presence of an additional gating-light source. Gating enhancement factors of 104 were observed. In BaClF+ this involves twostep photoionization of Sm2+ and leads to persistent holes in the 4F0 - 5D1 (687.9-nm) and 7F0 → 5D1 (629.7-nm) absorption lines. The hole widths of 25 MHz at 2 K are much narrower than the inhomogeneous broadening of 16 GHz. The action spectrum of the gating shows a threshold behavior around 2.5 eV. Erasing studies show that Sm3+ acts as a trap for the released electrons. A remarkable and novel feature is that the holes can be recovered after temperature cycling to 300 K. © 1985, Optical Society of America.