Fabrication and characterization of nanoscale, Er3+-doped, ultratransparent oxy-fluoride glass ceramics

Abstract

We show that oxy-fluoride glass ceramics, with typical composition, 32(SiO2):9(AlO1.5):31.5(CdF2):18.5(PbF2):5.5(ZnF2): 3.5(ErF3) mol % have potential applications in telecommunications. Upon heat treatment, Er3+ nucleates the growth of the nanocrystalline β-PbF2, which acts as its host. Heat treatment at 440 °C for 5 h and at 390 °C for 3 h gave rise to ∼12 and ∼2.5 nm diameter crystals, respectively. The emission band of Er3+ in the 1.54 μm telecommunications window (4I13/2→4I15/2 transition, at the half-height width) was 75 nm in the former and 90 nm in the latter case, while I13/24↔I15/24 absorption and emission bands became wavelength divergent in both cases. Also in the latter case, the spectrum was flat from 1.53 to 1.56 μm. The evolution of spectral behavior is explained by changes in average site geometry of the Er3+ dopant, related to the α→β phase transition of PbF2, which is stimulated by heat treatment.

Optical scattering in glass ceramics

“…A strong optical scattering, highly detrimental for applications, would be expected for these systems on the basis of the presence of particles, which have in general a different refractive index from the amorphous matrix where they are embedded. However many glass-ceramics, in particular those obtained from oxyfluoride glasses, have shown a transparency similar to that of glasses, much higher than that expected from the theory of Rayleigh scattering [2,3].…”

“…Their structure makes them valuable for application in photonics as they combine the spectroscopic properties of crystals with the mechanical properties of glasses [1][2][3][4][5]. A strong optical scattering, highly detrimental for applications, would be expected for these systems on the basis of the presence of particles, which have in general a different refractive index from the amorphous matrix where they are embedded.…”

Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics

“…It has been proved that F -interstitial mechanism is more stable and favorable for charge balance. 16,17 Thus, F -interstitial mechanism is adopted in the following discussion. Besides, a doped fluorite crystal unit cell calculated by F -interstitial mechanism has a general formula Pb 1−x RE x F 2+x in the PbF 2 -RE lattice.…”

“…Besides, it has been found that the concentration of RE 3+ has a linear relationship with the PbF 2 -RE cell parameters. 16,20 Fedorov et al give a general formula that can be used to estimate the mole fraction x of RE 3+ for Pb 1−x RE x F 2+x fluorite-type composition in solid solutions, 21,22 where…”

“…Based on our previous work, rare earth ions (RE 3+ ) doped oxyfluoride glass ceramics are multiphase materials, where RE 3+ doped lead fluoride nanocrystals are embedded in the oxide glassy matrix. 14,16 XRD (D/Max-2500, Rigaku using CuKα line) measurements were used to characterize the crystal structures of Tm 3+ doped nanocrystals. A spectrograph equipped with 150 W xenon lamps were used to record the emission spectra.…”