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Congruent LiNbO3 crystals doped with 5.5/1, 6/0.15, and 7/0.8 mol %/mol % of Zn/Er were thermally treated at 1120 °C over 101 h using vapor transport equilibration (VTE) technique. Unpolarized visible and infrared absorption spectra of the VTE-treated and corresponding as-grown crystals were recorded at room temperature. It is shown that VTE treatment has brought these crystals closer to stoichiometric composition. X-ray powder diffraction and optical absorption results show that the VTE treatment induces the crystalline phase transformation with respect to Er3+ from the original Er3+:LiNbO3 to the ErNbO4 in all crystals studied. The formation of the ErNbO4 phase results in substantial absorption changes that include the drop of the transparency in the visible region, the reduction of Er3+ absorption, and the Zn-doping-level-dependent changes in spectral shape and peaking position at 0.98 and 1.5 μm regions. Based upon the measured absorption spectra, the influences of Zn-doping level and VTE treatment on the Er3+ spectroscopic properties were studied by using the Judd-Ofelt (JO) theory. The results show that the VTE treatment has a little effect on the fluorescence branch ratio, while a large effect on the JO parameters, oscillator strength, and electron transition probability. The Zn doping level affects the JO parameters, oscillator strength, and transition probabilities of some individual manifolds. In addition, the VTE treatment leads to the increases of the theoretical radiative lifetimes of almost all manifolds considered. For the emission at 1.5 μm, the lifetime increase is as much as 30% and the theoretical results are in well agreement with the experimental data. The VTE-induced lifetime increase is qualitatively explained. [ABSTRACT FROM AUTHOR]

Two optimized methods for accurately measuring the 1.5 µm lifetime of Er[sup 3+] in LiNbO[sub 3] crystals and waveguides are proposed. The first method, suitable for measurement of bulk material, was suggested by forming an annealed proton exchanged sandwich structure and fluorescence was collected through an adjustable aperture. This excitation collection scheme was used to investigate bulk Er-doped LiNbO[sub 3] crystals with eight different Er[sup 3+] doping levels, three different crystal thicknesses, and three different cut orientations. The 1.5 µm lifetime was investigated in three configurations: with both a sandwich and an aperture, with a sandwich but without an aperture, and without not only a sandwich but also without an aperture. In addition, the effect of the aperture was also studied. The second method, suitable for a waveguide structure, was proposed on the basis of transversely gathering the fluorescence aided by an outcoupling fiber. It was optimized by comparing three different fluorescence collection schemes. Using this method, the lifetimes of some Ti: Er:LiNbO[sub 3] strip waveguides were measured. In addition, the effect of radiation trapping on the polarized fluorescence spectrum was also investigated. The experimental results are discussed and summarized. [ABSTRACT FROM AUTHOR]

Rare earth doped opaque aluminum tellurite ceramics exhibiting multicolor upconversion and color tunability have been synthesized and characterized. The multicolor fluorescence comprises of green, red, and blue upconversion emissions from Ho3+ and Tm3+ ions. By varying the intensity ratios between the upconversion emission bands, the fluorescence color can be tuned from multicolor to white color by changing the infrared wavelength pump power. The fluorescence color tunability in Ho3+/Tm3+/Yb3+ triply doped aluminum tellurite ceramics will lead to new applications in the field of multicolor fluorescence technology. [ABSTRACT FROM AUTHOR]

Multichannel transition emissions in Pr3+-doped fluorotellurite (4BaF2–4AlF3–16BaO–6La2O3–70TeO2, BABLT) glasses have been quantitatively characterized. Broadband ∼1.48 µm near-infrared (NIR) emission due to 1D2 → 1G4 transition covering a 1.28–1.68 µm wavelength region possesses a full-width at half-maximum of 120 nm, along with the spontaneous emission probability (Aij) and maximum stimulated emission cross-section (σem) are calculated to be 693 s−1 and 8.97 × 10−21 cm2, respectively. Intense visible fluorescence originating from 3P0 and 1D2 levels has been observed and the radiant flux for the visible fluorescence of Pr3+ is solved to be 299 µW under commercial blue LED excitation. Quantitative characterization reveals that Pr3+-doped BABLT glasses exhibit a quantum yield (QY) as high as 14.9%, which is 3.1% higher than that in Pr3+-doped heavy metal germanium tellurite glasses. High QY and broadband ∼1.48 µm emission illustrate great advantages of Pr3+-doped BABLT glasses as fibre luminescence sources in photodynamic therapy treatment and gain media for tunable lasers and NIR optical amplifiers. [ABSTRACT FROM AUTHOR]

Er 3+ doped Na2O–Nb2O5–TeO2 (NNT) glasses suitable for making optical waveguide devices has been fabricated and characterized. Intense 1.53 μm infrared fluorescence and green upconversion luminescence were observed under 975 nm diode laser and 798 nm laser excitation. The optical absorption, the Judd–Ofelt parameters and the spontaneous transition probabilities have been measured and calculated. The quantum efficiency of 1.53 μm emission band is proved to be ~100%. The maximum emission cross-section is 1.02×10-20 cm2 at 1.533 μm, and it is more than 30% higher than the values in silicate and phosphate glasses. Under 798 nm excitation, strong green and weak red upconversion luminescence was observed at room temperature. The 546 nm green band shows a broad full-width at half-maximum of 16 nm. Intense and broad green upconversion fluorescence in Er 3+ doped NNT glass can be used in colour display, undersea communication and infrared sensor. High concentration of Na2O is a benefit to developing waveguide device from the glass. [ABSTRACT FROM AUTHOR]