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We present the case of photoionization-induced persistent spectral holeburning in rare earth doped II-VI compounds for high density memory storage. Experimental data on photon-gated holeburning has been presented for different sulfide hosts (MgS, CaS: RE2+ and RE3+). With the proper choice of the host electronic band structure, the optically active rare earth ion and its electronic transitions involved in the holeburning process, we have observed the highest number of persistent holes ever burned in a single electronic transition. Efficient photon-gated holeburning in the 4f7 (8S7/2) - 4f65d1 transition of Eu2+ is a result of photoionization of Eu2+ to Eu3+. These holes have a width of less than 5 GHz, have no detectable erasing effects after thousands of reading cycles, survive thermal cycling up to the room temperature and have infinite lifetime at low temperature (2 K). Although self- gated holeburning is observed with reading laser at higher powers, the photon budget for reading these holes is so small that thousands of reading cycles can be performed without significantly affecting the optical signal. We discuss the unique features of these systems that make them the most promising candidates to date for the holeburning based optical memories.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
