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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]

We have measured the polarized visible and near-infrared, and unpolarized mid-infrared (2.7 \mum) emission spectra of photorefractive-damage-resistant locally Er-Mg-doped near-stoichiometric (NS) Ti:Mg:Er:LiNbO3 strip waveguide, fabricated on an X-cut initially congruent LiNbO3 substrate in sequence by local Er doping in air, Mg-Ti pre-diffusion in wet O2 and post Li-rich vapor transport equilibration treatment. From the measured emission spectra, the emission and absorption cross section spectra were calculated based upon McCumber theory. The spectroscopic features are discussed in comparison with the spectra recorded from the area outside the waveguide, and with the previously reported results of bulk-doped NS Er:Mg:LiNbO3 crystals and congruent Er:LiNbO3 bulk material or Ti:Er:LiNbO3 waveguide structure. The results show that the spectra of the NS waveguide are traditional and reveal small differences from those spectra outside the waveguide in spectral shape, polarization dependence, as well as cross section values. In contrast, the cross section values of the NS waveguide show considerable differences from those of bulk-doped NS material and congruent bulk material or waveguide structure. The 552, 673, 996, and 1531 nm emission lifetimes of the Er^3+ ions outside the waveguide were also measured, and found to be comparable to the results of the bulk-doped NS crystal and the congruent bulk material or waveguide structure. [ABSTRACT FROM PUBLISHER]

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]

Abstract: We have measured OH absorption spectra of a 0.47-mm-thick Z-cut MgO (5mol% in melt):LiNbO3 crystal subjected to post-growth Li-poor vapor transport equilibration (VTE) treatments at 1100°C for different durations ranging from zero to 395h. These spectra allow the evolution of OH absorption characteristics with prolonged VTE to be followed. After 2h of VTE process an additional absorption appears at 3483cm−1. A transition regime that the original 3536cm−1 and new 3483cm−1 absorptions simultaneously appear exists within the VTE duration range of 2–16h. In this regime, the 3536cm−1 absorption becomes weak gradually and eventually disappears around 16h while the 3483cm−1 absorption increases remarkably with the prolonged VTE. The presence of transition regime gives a hint that the 3483cm−1 absorption is due to the VTE-induced formation of a new center. Based upon the spectral features, we have suggested a simple three-layer (two on surface and one in the center of crystal plate) model to describe the depth profile of the photorefractive damage MgO concentration threshold in the crystal in the transition regime. A Li out-diffusion theory is suggested and correlated with the model. To support the Li out-diffusion theory, some additional experiments have been done. These include the depth profile characterization of VTE-induced Li2O content reduction and the measurement of the surface Li2O content as a function of the VTE duration. A quantitative analysis and discussion shows that the model is well supported by the experimental results. [Copyright &y& Elsevier]