Persistent high density spectral holeburning in CaS:Eu and CaS:Eu,Sm phosphors

Persistent spectral hole-burning has been reported for singly, flu-doped, 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+ is a result of photoionization of Eu2+ to Eu3+. These holes have a width of <5 GHz (2 K), survive thermal cycling of the phosphor up to the room temperature, 300 K, and have no detectable deterioration over more than a day of storage time at low temperature (2 K). Although self-gated holeburning is observed with the reading laser at higher powers, the photon budget for reading these holes is so small that in excess of 1000 reading cycles can De performed without destroying the optical signal. The nature of holes burned by photon-gating is found to be very different from the self-gated holes. The characteristics for the holeburning 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 density optical memory storage using photon-gated holeburning in this THz broad transition are discussed. (C) 1998 American Institute of Physics. [S0003-6951(98)02019-1].