Persistent spectral hole burning has been observed on the zero-phonon lines of the main site and several perturbed sites of ${\mathrm{Eu}}^{2+}$ in CaS:Eu single crystals. Hole burning occurs by two-step photoionization, can be strongly gated with IR irradiation, and takes place by excited-state absorption from the metastable ${4f}^{6}5d$ excited state to the conduction band followed by electron transport to ${\mathrm{Eu}}^{3+}$ centers which are the dominant traps. A complex hole structure consisting of a narrow feature (200 MHz), and broader features ($\ensuremath{\approx}5$ and $\ensuremath{\approx}100\mathrm{GHz}$) is observed. A mechanism is described for the occurrence of these unusually broad features. Time-varying internal electric fields which occur during the hole burning due to photoionization and trapping can lead to burning of holes at frequencies non-resonant with that of the laser. In addition, a mechanism for hole erasure, tunneling between Eu ions, is demonstrated. This mechanism is identified from the frequency dependence of the hole erasure which follows the ${\mathrm{Eu}}^{2+}$ absorption, and the linear dependence of the photoconductivity and hole erasure efficiency on irradiation power, both of which indicate erasure in a single-photon process.Persistent spectral hole burning has been observed on the zero-phonon lines of the main site and several perturbed sites of ${\mathrm{Eu}}^{2+}$ in CaS:Eu single crystals. Hole burning occurs by two-step photoionization, can be strongly gated with IR irradiation, and takes place by excited-state absorption from the metastable ${4f}^{6}5d$ excited state to the conduction band followed by electron transport to ${\mathrm{Eu}}^{3+}$ centers which are the dominant traps. A complex hole structure consisting of a narrow feature (200 MHz), and broader features ($\ensuremath{\approx}5$ and $\ensuremath{\approx}100\mathrm{GHz}$) is observed. A mechanism is described for the occurrence of these unusually broad features. Time-varying internal electric fields which occur during the hole burning due to photoionization and trapping can lead to burning of holes at frequencies non-resonant with that of the laser. In addition, a mechanism for hole erasure, tunneling between Eu ions, is demonstrated. This mechanism is identified from the frequency dependence of the hole erasure which follows the ${\mathrm{Eu}}^{2+}$ absorption, and the linear dependence of the photoconductivity and hole erasure efficiency on irradiation power, both of which indicate erasure in a single-photon process.

Physical review. B, Condensed matterNov 15, 199721 citations

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

Z. Hasan, Michael G. Solonenko, P. I. Macfarlane +3 more

Persistent spectral hole-burning has been reported for singly, Eu-doped, and doubly, Eu- and Sm-doped, CaS phosphors. 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 <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 be 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.Persistent spectral hole-burning has been reported for singly, Eu-doped, and doubly, Eu- and Sm-doped, CaS phosphors. 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 <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 be 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.

Applied Physics LettersMay 11, 199839 citations

Transient and photon-gated persistent spectral holeburning in CaSO4:Sm

Robert J. Danby, Keith Holliday, Neil B. Manson

Journal of LuminescenceAug 1, 198815 citations

Persistent spectral hole burning has been observed on the zero-phonon lines of the main site and several perturbed sites of

{\mathrm{Eu}}^{2+}

in CaS:Eu single crystals. Hole burning occurs by two-step photoionization, can be strongly gated with IR irradiation, and takes place by excited-state absorption from the metastable

{4f}^{6}5d

excited state to the conduction band followed by electron transport to

{\mathrm{Eu}}^{3+}

centers which are the dominant traps. A complex hole structure consisting of a narrow feature (200 MHz), and broader features ($\ensuremath{\approx}5$ and $\ensuremath{\approx}100\mathrm{GHz}$) is observed. A mechanism is described for the occurrence of these unusually broad features. Time-varying internal electric fields which occur during the hole burning due to photoionization and trapping can lead to burning of holes at frequencies non-resonant with that of the laser. In addition, a mechanism for hole erasure, tunneling between Eu ions, is demonstrated. This mechanism is identified from the frequency dependence of the hole erasure which follows the

{\mathrm{Eu}}^{2+}

absorption, and the linear dependence of the photoconductivity and hole erasure efficiency on irradiation power, both of which indicate erasure in a single-photon process.