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Miscible-order fluoride-phosphate blocky phosphor (FBP), composed with ordered-phase of NaYF4 crystals and unordered phase of tin-fluorophosphate glass, is prepared by a two-step process and luminescent properties of FBPs embedded with different particle sizes of NaYF4 crystals are presented. High-frequency fluorescence from higher metastable 5DJ (J = 1, 2 and 3) energy levels are effectively released in Eu3+ doped fluoride crystals. Taking the blue emission of Sn2+ as the framework, multi-peak emissions from metastable energy levels are controlled to adjust the color coordinates of the FBP to the white-light region, which the color rendering index (CRI) reaches 89. Tunable color FBP with high CRI retains splendid luminescence property of fluoride, providing a potential candidate for the development of white LED. [ABSTRACT FROM AUTHOR]

Er3+-doping effect on electro-optic property of LiNbO3 crystal has been studied. A series of congruent LiNbO3 crystals homogenously doped with different Er3+ concentrations up to 2 mol% in melt were grown. Unclamped electro-optic coefficients r 13 and r 33 of these crystals were measured by Mach–Zehnder interferometry. The results show that both r 13 and r 33 reveal little dependence on Er3+ doping level. r13 hardly changes in the studied Er3+ doping level range 0–2 mol% within the experimental error of 3%. r33 reveals a degradation tendency with a rise in the Er3+ doping level, but the degradation is no more than 5% in the Er3+ doping level range studied. The small effect is consistent with previous result that the performance of an electro-optic device based on Ti4+-diffused Er3+-doped LiNbO3 waveguide is not influenced noticeably by Er3+-doping. A qualitative, comprehensible explanation is given for the small effect. [ABSTRACT FROM PUBLISHER]

We report a Ti:Er:LiNbO3 strip waveguide with high diffusion-doped surface Er3+ concentration. The waveguide was fabricated with a technological process in sequence of preparation of noncongruent, Li-deficient LiNbO3 substrate by performing Li-poor vapor transport equilibration treatment on a congruent Z-cut LiNbO3 plate, diffusion of 40-nm-thick Er metal film, and fabrication of 8-μm-wide Ti-diffused strip waveguide. The waveguide retains the LiNbO3 phase and shows the waveguiding characteristics similar to the conventional Ti:LiNbO3 waveguide. Secondary ion mass spectrometry study shows that the Er3+ diffusion reservoir was exhausted and the profile is Gaussian with a surface concentration two times larger than that of the conventional Ti:Er:LiNbO3 waveguide. The waveguide shows stable 1547-nm small-signal enhancement under the 1480-nm pumping without serious optical damage observed, and a 5-dB signal enhancement is obtained for the available coupled pump power of only 90 mW. A saturated net gain as much as 5 dB/cm is predicted theoretically. [ABSTRACT FROM PUBLISHER]

We report optical-damage-resistant Ti:Er:LiNbO3 strip waveguide with high diffusion-doped surface Er^3+ concentration. The waveguide was fabricated starting from a commercial X-cut congruent LiNbO 3 plate with a two-step technological process in sequence of simultaneous work of Er^3+ diffusion doping and Li-poor vapor transport equilibration treatment, and fabrication of 6-μm-wide Ti-diffused strip waveguide (Z-propagation). The waveguide retains still the LiNbO3 phase and has the waveguiding characteristics similar to the conventional Ti:LiNbO3 waveguide except with a larger loss due to the imperfection of waveguide. Secondary ion mass spectrometry study shows that the Er^3+ diffusion reservoir was exhausted and the profile is the desired Gaussian-type with a surface concentration 1.0 mol%, which is about two times larger than the value of conventional Ti:Er:LiNbO3 amplifier. Further optical characterization shows that the waveguide shows stable 1547 nm small-signal gain under the 980 nm pumping without serious photorefractive effect observed. An unsaturated gain 1.7 dB/cm is obtained for the available coupled pump power of 160 mW. With increased pump power, optimized Er ^3+ diffusion condition and degraded loss figure, a higher gain is expected. [ABSTRACT FROM PUBLISHER]

Co-diffusion characteristics of Er3+ and Tm3+ ions in LiNbO3 crystal have been studied, together with two other properties: doping effect on refractive index of substrate, and Li out-diffusion. Er3+/ Tm3+-codoped LiNbO3 single-crystals were prepared by co-diffusion of stacked Er- and Tm-metal thin films, coated onto parts of the surfaces of X- and Z-cut congruent LiNbO3 crystal plates, at different temperatures and different durations in air. After diffusion, the surface refractive indices of the doped and undoped parts were measured by prism coupling technique, and the surface composition was evaluated from the measured indices. The results show that the dopings have negligible effect on the substrate index and the Li out-diffusion depends mainly on the diffusion temperature. The Er3+ and Tm3+ profiles were studied using secondary ion mass spectrometry, and a co-diffusion dynamical model is proposed and verified experimentally. From the measured profiles, the temperature-dependent Er3+/ Tm3+ diffusivity and solubility were obtained together with other relevant parameters, such as diffusion constant, activation energy, solubility constant and heat of solution. The Er3+ and Tm3+ co-diffusion exhibits similar temperature dependent diffusivity, and the dependence is similar to that of single-diffusion. In the co-diffusion case, the total solubility consists of two parts: Er3+ and Tm3+ parts, there is no anisotropy, and the value is equal to that of single-diffusion case, in which both ions have the similar solubility. The Er3+ and Tm3+ parts of solubility change relatively with the initial metal film thicknesses and hence have different temperature dependences. Nevertheless, their sum, i.e., the co-diffusion solubility, remains a constant at a given temperature. [ABSTRACT FROM AUTHOR]

We have measured at room temperature polarized visible and near-infrared and unpolarized mid-infrared (2.7 µm) emission spectra of Er3+ in LiNbO3 (LN) crystals grown from congruent melts doped with 0.0/0.5, 0.5/0.5, and 1.0/0.5 mol%/mol% In2O3/Er2O3. From the measured emission spectra, the emission and absorption cross section spectral distributions were analyzed based on McCumber theory and discussed in comparison with those spectra of only Er-doped LN bulk material and/or Ti: Er: LN waveguide structure and with the results from the unpolarized absorption measurements. For the 530 and 1530 nm transitions, the cross section value, polarization dependence, and spectral shape all change from the only Er-doped material to the In-Er-codoped crystal and show definite In2O3 doping level effect. The 559, 673, 996, and 1530 nm emission lifetimes were also measured and used to evaluate nonradiative multiphonon relaxation rate. The calculated radiative, measured lifetimes, and multiphonon relaxation rate also show In-codoping effects. [ABSTRACT FROM AUTHOR]

Congruent Er:Mg:LiNbO3 crystals were grown by the Czochralski method from the melts containing fixed 0.5 mol% Er2O3 while varied MgO content ranged from 0.0 to 8.0 mol%. The Mg and Er contents in the crystals were determined by neutron activation analysis. In the presence of Er codopant, the Mg threshold concentration with respect to optical damage is determined from the measured OH absorption spectra. The results show that the Er codopant has less effect on both the Mg threshold concentration and Mg segregation coefficient, which is within 1.13–1.23 as the Mg concentration is below the threshold while within 0.88–0.98 when above the threshold, consistent with the only MgO doping case. On the other hand, the practical Er concentration in the crystal is closely related to the Mg content and shows definite Mg threshold effect. Below the threshold, the Er concentration decreases linearly with the increased Mg concentration in the crystal; above the threshold, the decrease is more remarkable and follows another linear function. The Mg concentration effect on the Er segregation coefficient is discussed from the viewpoint of the Mg doping effect on the solubility of Er ions in the crystal. [ABSTRACT FROM AUTHOR]

Diffusion characteristics of Zr4+ in LiNbO3 single-crystal were studied. Zr4+-doped LiNbO3 crystal plates were prepared by in-diffusion of 100 nm thick ZrO2 film coated onto Z-cut congruent substrates in wet O2 at different temperatures. Zr4+-diffused profile was analyzed by secondary ion mass spectrometry. The results show that the Zr4+ diffusion follows the traditional diffusion theory. From the measured profiles, important diffusion parameters are obtained, such as diffusivity and its temperature dependence, diffusion constant, activation energy, surface concentration, and solubility. The Zr4+ has a diffusivity similar to that of Ti4+, implying that the Zr4+ doping and the Ti4+ diffusion can be performed simultaneously to simplify the fabrication process of a photorefractive-damage-resistant Zr4+-doped Ti-diffused LiNbO3 waveguide. [ABSTRACT FROM AUTHOR]

The influence of Li-rich vapor transport equilibration ( VTE) on surface Li2 O-content of 1-mm-thick, congruent X-, and Z-cut LiNbO3 crystal plates was studied against the VTE temperature. The VTE-induced surface Li2 O-content increase was evaluated from measured birefringence. The results show that the increase follows the traditional Arrhenius law with a surface Li2 O-content alteration constant (614 ± 136)/(91 ± 10) mol% and an activation energy (0.76 ± 0.05)/(0.53 ± 0.03) eV for the X/ Z-cut plate. An empirical expression that correlates the VTE-induced surface Li2 O-content alteration with both the VTE temperature and duration is presented. The expression is useful for producing a near-stoichiometric LiNbO3 plate with the desired surface Li2 O-content via balancing the VTE temperature and duration. [ABSTRACT FROM AUTHOR]

We report that the polarization property of \Er^3+ transition in \LiNbO3 waveguide or bulk material is closely related to the incident direction of excitation beam relative to the optical axis of the crystal. It is found that the 1.5-\mu\m transition is highly \sigma- (\pi-) polarized as the excitation direction is perpendicular (parallel) to the optical axis, and the 0.67-\mu\m transition reveals a reversed effect. Incident perpendicularly (parallel), the transition is highly \pi- (\sigma-) polarized. The effect is found to be independent of the polarization state and wavelength of the excitation light. It is attributed to the selective Er site excitation. [ABSTRACT FROM PUBLISHER]

Clamped and unclamped electro-optic coefficients γ 13 and γ 33 of In 3+ /Er 3+ -codoped LiNbO 3 crystals, which were grown by Czochralski method from the melts containing 0.5 mol% Er 2 O 3 while varied In 2 O 3 contents of 0.0, 0.5, 1.0 and 1.5 mol%, were measured by Mach-Zehnder interferometry. The results show that In 3+ /Er 3+ codoping does not cause change of γ 13 and γ 33 , and both γ 13 and γ 33 can be regarded as unchanged in the studied In 3+ concentration range of 0–2.6 mol% (in crystal) within the experimental error of 3%. The small doping effect is desired in light of the electro-optic application of the crystal. A qualitative, comprehensible explanation for the small effect is given on the basis of the EO coefficient model of LiNbO 3 and doping effect on the defect structure of LiNbO 3 . [ABSTRACT FROM AUTHOR]