Spectral hole burning in the 4f–5d transition of Ce3+ in LuPO4 and YPO4

Persistent spectral holes in the inhomogeneously broadened 4f1–4f05d1 zero-phonon transitions in LuPO4:Ce3+ and YPO4:Ce3+ crystals were burned at T=2 K. The holes observed in absorption were deep (up to 50%) and could be observed at least minutes after they were burned. The burning process was very efficient and is due to a single photon process. The observed spectral holes are burned in a photochemical process of photoionization of Ce3+ ions involving electron tunneling from Ce3+ centers to traps.