Room-temperature Persistent Spectral Hole Burning Research Articles

Room Temperature Persistent Spectral Hole-Burning in Sol-Gel-Derived Glasses Doped with Eu3+ Ions

Persistent spectral hole burning was investigated for the Eu3+ ions-doped glasses prepared by a sol-gel method. For the glasses containing OH bonds, persistent spectral hole is burned by the laser-induced rearrangement of the OH bonds surrounding the Eu3+ ions, which is thermally unstable to erase up to ∼200 K. On the other hand, the Eu3+-doped Al2O3-SiO2 glasses which are heated under H2 gas or irradiated with X-ray exhibit room temperature PSHB. The depth of the burnt hole increases as the Al2O3 content increases. The hole-formation could be explained by a model of the excitation of the Eu3+ ions and subsequent electron transfer with the excited [Eu3+]− or oxygen-defect centers in the Al—O bonds. The burnt holes are more stable compared with those burned by the rearrangement of the OH bonds.

Mechanism of the room-temperature persistent spectral hole burning in borate glasses doped with Eu3+

Spectroscopic properties and room-temperature persistent spectral hole burning mechanisms of Eu3+-doped borate glasses were investigated. The depth of the burnt hole increased with the amount of carbon powders (i.e., degree of reducing atmosphere). This was attributed to the formation of defects which can donate free electrons for the photoreduction of Eu3+→Eu2+. Holes survived >104 s at 20 K and approximately 40% of hole areas were preserved after annealing at 280 K. The photoreduction of Eu3+ to Eu2+ is a primary mechanism of hole burning and this hypothesis was supported by spectral hole properties, relaxation properties as well as changes in the local structure of Eu3+ in glasses.

Ultrashort-laser-pulse-induced persistent spectral hole burning of Eu^3+ in sodium borate glasses

We have observed persistent spectral hole burning (PSHB) in Eu(3+) -doped sodium borate glasses irradiated with near-IR femtosecond laser pulses. As-prepared glasses, i.e., glasses melted in air, do not show PSHB even at low temperatures (~77K) , but room-temperature PSHB occurs in the irradiated glasses. The exposure to IR radiation causes both the reduction of Eu(3+) to Eu(2+) and the formation of intrinsic defects. We propose that the photoinduced redistribution of electric charges between Eu(3+) to Eu(2+) is responsible for the occurrence of PSHB.

Room temperature persistent spectral hole burning in x-ray irradiated Eu3+-doped borate glasses

Irradiation of x-rays has induced room-temperature persistent spectral hole burning (PSHB) in Eu3+-doped borate glasses melted under an inert atmosphere. Defects were formed by x-ray irradiation and these defects, especially electron trapping centers near rare-earth ions in glasses, were responsible for the PSHB. Electrons were released from these defects upon irradiation of a burning light. Photoreduction of Eu3+ to Eu2+ by trapping these electrons resulted in the formation of persistent spectral holes.

Room-temperature photochemical hole burning of Eu3+ in sodiumborate glasses

Persistent spectral hole burning (PSHB) has been observed at 77 K to roomtemperature for Eu3+ in sodium borate glasses with compositions of xNa2O·(100-x)B2O3 (x = 10,25,35). Glasses meltedin air do not show the phenomenon of PSHB, while room-temperature PSHB occursin the glasses prepared by melting in reducing conditions. 151EuMössbauer spectra reveal that europium ions are present as both Eu3+and Eu2+ in glasses melted in reducing conditions. The relative hole areaincreases with an increase in the molar ratio of Eu2+ to Eu3+ whenthe content of Eu2+ is low, whereas the relative hole is almostindependent of the molar fraction of Eu2+ when the content of Eu2+is high. Furthermore, a comparison of hole burning among sodium borate glasseswith the molar fraction of Eu2+ being almost the same as one anothershows that the hole area grows larger as the content of Na2O becomeshigher. These observations are interpreted in terms of the photoinducedredistribution of electric charges between Eu3+ and Eu2+. The effectof the glass composition on hole widths is also discussed based on thestructural change in sodium borate glasses.

Room-temperature persistent spectral hole burning ofEu3+coupling withAl3+in glass

Room-temperature persistent spectral hole burning was observed in ${\mathrm{Eu}}^{3+}\ensuremath{-}\mathrm{d}\mathrm{o}\mathrm{p}\mathrm{e}\mathrm{d}$ ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}{\ensuremath{-}\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ glasses. The sol-gel-derived ${\mathrm{Eu}}^{3+}\ensuremath{-}\mathrm{d}\mathrm{o}\mathrm{p}\mathrm{e}\mathrm{d}$ glasses were heated in hydrogen gas and irradiated with x ray, in which the oxygen deficient centers were induced in Al-O bonds and some ${\mathrm{Eu}}^{3+}$ ions were reduced into ${\mathrm{Eu}}^{2+}$ by heating in hydrogen gas. The spectral holes were burned in the excitation spectra of the ${}^{7}{\stackrel{\ensuremath{\rightarrow}}{{F}_{0}}}^{5}{D}_{0}$ transition of ${\mathrm{Eu}}^{3+}.$ The maximum depth of the hole burned at room temperature was found to be $\ensuremath{\sim}10%$ of the total excitation intensity for both the glasses and independent of the treatment conditions of glasses. A proposed model for hole burning is the excitation of the ${\mathrm{Eu}}^{3+}$ ion and subsequent hole trapping in the oxygen-defect centers in the Al-O bonds. The burnt holes were easily erased by laser irradiation with the energy different from burning one.

Room-temperature persistent spectral hole burning of x-ray-irradiatedSm3+-doped glass

We report on persistent spectral hole burning in the x-ray-irradiated Sm3+-doped fluoroaluminate glasses at room temperature. 0.1SmF3·14.9YF3·10MgF2·20CaF2 10SrF2·10BaF2·35AlF3 (mol%) glass was prepared underan Ar + NF3 (5 vol.%) atmosphere. Absorption andphotoluminescence spectra showed that some of the Sm3+ ions in theglass sample were reduced to Sm2+ ions after the x-ray irradiation.The hole was burned in the 7F0-5D0 line of the Sm2+ ions by means of a DCM dye laser. No antihole or increasedexcitation (absorption) peak was observed around the burned hole. It wasconcluded that the persistent spectral hole burning was formed by theoptically activated recombination of the electrons trapped by the Sm3+ ions with the trapped holes.

Room-temperature persistent spectral hole burning in Eu 3+-doped inorganic glasses: the mechanisms

High-temperature persistent spectral hole burning (PSHB), up to room temperature, has been observed in a Eu 3+-doped aluminosilicate glass and in a lanthanum-aluminosilicate one. The emphasis here is on trying to understand the mechanism(s) leading to such a process and the effects due to changes in glass composition. Spontaneous refilling measurements show that at least two mechanisms, a very slow one and a faster one, are involved. The “faster” or “easy” component may correspond to a local structural rearrangement of the host and/or to photoreduction of the Eu 3+ ions. We suggest that the slow component, leading to very stable photoproducts, corresponds to transfer of an electron over a sizable distance through a multi-step process. PSHB in the lanthanum-aluminosilicate sample requires larger irradiation doses but leads to more stable spectral holes. This observation is discussed, which leads us to raise the question as to whether there should be a trade-off between easiness and stability.

Room-temperature persistent spectral hole burning of Sm 2+ in silica-based fibers

Persistent spectral hole burning has been observed successfully at room temperature in the excitation spectrum for the 7 F 0− 5 D 0 transition of Sm 2+ in silica-based fibers co-doped with Al. The room-temperature persistent spectral hole burning is reported for the first time, to the best of our knowledge, in Sm 2+-doped fiber. The hole width was measured to be about 6 cm −1. The ratio of inhomogeneous to homogeneous linewidths of this system is ∼15.

Room-temperature persistent spectral hole burning of Eu^3+ in sodium aluminosilicate glasses

Persistent spectral hole burning has been observed at 77 K, 180 K, and room temperature for Eu(3+) in sodium aluminosilicate glass melted under a reducing atmosphere. In particular, room-temperature persistent spectral hole burning is reported for the first time to our knowledge in Eu(3+) -doped materials. The persistent hole is accompanied by no antiholes and lasts for 1 h at least. The thermal stability of the hole is greater than that of a persistent hole burned for Eu(3+) in sodium aluminosilicate glass melted in air.

Persistent spectral hole burning of Sm2+ in borate glasses

It is expected that persistent spectral hole burning (PSHB) will be applied for a high-density data storage system and it can serve as a powerful method for studying the local structure around optical centers. The authors' group has discovered a room-temperature PSHB material for Sm2+-doped glasses. The present work investigated the relationship between the Debye temperature of the glass and the hole width, and the effects of alkali ions on hole burning for alkali borate glasses. Sm2+-doped glasses were produced in a strongly reducing atmosphere. Hole burning was measured for the 5D0-7F0 transition of the Sm2+ ion. The hole width decreased with increasing Debye temperature which is a parameter of the bond strength of glass network former. The hole width for borate glasses was more closely related to the local structure around the Sm2+ ion than to the glass matrix. The hole depth increased with increasing optical basicity of glasses. The hole burning mechanism in Sm2+-doped glasses seemed to be the photo-ionization of Sm2+ → Sm3+ + e−.