Articles you may be interested inSpectroscopic and upconversion properties of erbium-doped potassium lithium tantalate niobate crystals under 800 nm femtosecond laser excitation J. Appl. Phys. 108, 043520 (2010); 10.1063/1.3475511Judd-Ofelt analysis of spectroscopic property of Er 3 + in congruent and near-stoichiometric Zn ∕ Er -codoped Li Nb O 3 crystals Z-cut MgO heavily codoped ͑6 mol % ͒ Er͑0.4 mol % ͒ : LiNbO 3 crystals were thermally treated at 1110 and 1120°C over 100, 120, and 220 h using vapor transport equilibration ͑VTE͒ technique. Visible and infrared-absorption and x-ray powder diffraction have been used to characterize their spectral, spectroscopic, and crystalline phase characteristics in comparison with the as-grown crystal. The experimental results show that VTE treatment results in the reduction of background absorption and 4 -5-nm blueshift of the optical-absorption edge, qualitatively showing that these crystals have been brought closer to stoichiometric composition. The VTE procedure also results in remarkable Er 3+ absorption changes. These spectroscopic changes imply that the VTE treatment may result in the formation of ErNbO 4 precipitates in all VTE crystals. In addition, the VTE treatment also results in substantial spectral changes with respect to OH − absorption. These OH − spectral changes are explained from the viewpoint of VTE-induced site-occupancy alterations of intrinsic and extrinsic defects. Based upon the measured absorption spectra, the influences of VTE treatment on the Er 3+ spectroscopic parameters were studied by using the Judd-Ofelt ͑JO͒ theory. The theoretical results show that VTE treatment has a little influence on the branch ratio, and a substantial influence on JO parameters and electron transition probability because of the phase transformation with respect to Er 3+ . The VTE treatment results in the increase of the JO parameters by more than 50% and theoretical radiative lifetime by 50%-120%.

A Raman scattering study was performed on ErNbO4 powder prepared by thermally calcining the mixture of 50 mol% Er2O3 and 50 mol% Nb2O5 powder at 1100 °C and 1600 °C over different durations. The scattering features are summarized and discussed. In combination with X‐ray diffraction results some useful information on the preparation of the ErNbO4 powder was obtained. A simple formation mechanism for ErNbO4 powder phase was suggested on the basis of an elevated‐temperature‐assisted solid‐state chemical reaction: Er2O3 + Nb2O5 ⇔︁ 2ErNbO4. A Raman study was also performed on some samples powdered from vapor‐transport‐equilibrated (VTE) Er(2.0 mol%):LiNbO3 crystals, in which nanocrystalline ErNbO4 was induced by the VTE procedure. A comparison of the spectra of the crystal‐powdered samples with those of directly calcined powder revealed that Raman peaks observed in the calcined powder cannot be resolved in either the single crystal or the crystal‐powdered sample due to the lower content of the ErNbO4 phase in the crystal. Present Raman results on powdered crystal support our earlier work on the assignment of the phonon modes in LiNbO3 crystals. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A number of X‐, Y‐ and Z‐cut Er(/Yb):LiNbO3 crystals with six different doping levels of rare earth ions were annealed at 1110 °C for 120 h using the vapor transport equilibration (VTE) technique. At room temperature, α‐polarized or unpolarized absorption spectra of these VTE‐treated crystals and corresponding as‐grown crystals were recorded in the wavelength range 280–1700 nm. The absorption characteristics of the VTE‐treated crystals are summarized and compared with those of the as‐grown crystals. The (Li+ + RE3+)/Nb5+(RE3+ = Er3+ or Er3+ + Yb3+) ratios in the VTE‐treated Er(/Yb):LiNbO3 crystals were evaluated using the optical absorption edge or Raman linewidth of the 153 cm–1 E(TO) phonon. Based upon the measured spectral data, spectroscopic parameters of Er3+ ions in as‐grown and VTE‐treated crystals were calculated using the Judd–Ofelt (J–O) theory. The influences of Er3+ doping level, type of crystal cut and VTE treatment on the key spectroscopic parameters, including integrated absorption coefficient, oscillator strength, J–O parameters and radiative lifetimes of three dominant emission manifolds (4I13/2 (∼1530 nm), 4F9/2 (∼660 nm) and 4S3/2 (∼560 nm)), are discussed and summarized and compared with the results for as‐grown crystals. The results for as‐grown crystals are also compared with those reported previously. The present theoretical result concerning the VTE effect on the 1530 nm lifetime is in rough agreement with the experimental result reported previously. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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