PERSISTENT HIGH-DENSITY SPECTRAL HOLEBURNING IN CAS-EU AND CAS-EU,SM PHOSPHORS

Persistent spectral hole-burning has been reported for singly, flu-dop ed, and doubly, Eu-and Sm-doped, CaS phosphors. Efficient photon gated holeburning in the 4f(7) (S-8(7/2)) - 4f(6)5d(1) transition of Eu2+ i s a result of photoionization of Eu2+ to Eu3+. These holes have a widt h of <5 GHz (2 K), survive thermal cycling of the phosphor up to the r oom temperature, 300 K, and have no detectable deterioration over more than a day of storage time at low temperature (2 K). Although self-ga ted holeburning is observed with the reading laser at higher powers, t he photon budget for reading these holes is so small that in excess of 1000 reading cycles can De performed without destroying the optical s ignal. The nature of holes burned by photon-gating is found to be very different from the self-gated holes. The characteristics for the hole burning are the same in singly and doubly doped phosphors, suggesting that under the conditions of our experiments, Sm traps do not play any significant role in spectral holeburning. Possibilities of high densi ty optical memory storage using photon-gated holeburning in this THz b road transition are discussed. (C) 1998 American Institute of Physics. [S0003-6951(98)02019-1].