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

Abstract

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.

Synthesis and properties of submicron range CaSO4:Eu particles

“…4(b) shows the same crystal with focus on crystal. The absorption of CaS:Eu 2+ is in visible region [24,25] and the emission in red. It is, therefore, surmised that the particles are the inclusions of CaS:Eu 2+ particles inside CaSO 4 particles.…”

Laser cooling of solids containing local centers with electric dipole allowed transitions: a feasibility study

“…The absence of cooling may be attributed to different mechanisms of laser heating that are competitive with cooling. (1) The most likely reason is that the excited state absorption is possible resulting in the electron transition from Eu 2+ ions in 4f 6 5d 1 state to the conduction band [19][20][21]. The energy of photons absorbed in the second step of this two-step photoionization process is mostly converted into heat in the course of the free electron relaxation.…”

“…4. These typical electron-phonon band spectra [9] overlap around the zero-phonon line wavelength (k = 625.5 nm at low temperatures [20,21]). It may be seen that the long-wavelength tail of the absorption spectrum allows excitation of Eu 2+ ions by photons with energy well below that of the emission maximum.…”

Nuclear forward scattering vs. conventional Mössbauer studies of atomically tailored Eu-based materials

“…Samples of MgS doped with varying concentrations of Eu were prepared by the methods described elsewhere [8,9]. The laser-excited fluorescence spectra at ∼15 K gave strong 4f 7 -4f 6 5d 1 emission confirming the presence of Eu 2+ in the sample.…”