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Diffusion properties of Sc3+ in LiNbO3 crystal were studied, together with other two related issues: Sc3+‐doping effect on LiNbO3 refractive index and Li2O out‐diffusion arising from Sc3+ in‐diffusion. To reach the goal, some Sc3+‐doped LiNbO3 crystal plates were prepared by in‐diffusion of Sc2O3 film coated onto Z‐cut congruent substrates in air at different temperatures ranging from 1030°C to 1130°C. After diffusion, the refractive indices at the doped and undoped parts of surface were measured by prism coupling technique and the surface composition was evaluated from the measured index. The results show that the Sc3+ doping has little contribution to the substrate index and the Li2O out‐diffusion is not measurable. The Sc3+ profile was analyzed by secondary ion mass spectrometry. Some characteristic parameters such as temperature‐dependent diffusivity, diffusion constant, activation energy, and surface concentration are obtained. The Sc3+/Ti4+ co‐diffusion characteristics were also studied. Comparison shows that in the single‐diffusion case, the Sc3+ diffusivity is considerably smaller than the Ti4+ diffusivity. In the Sc3+/Ti4+ co‐diffusion case, the Ti4+ co‐diffusion results in substantial increase in Sc3+ diffusivity while the Ti4+ diffusivity changing little. The diffusion characteristics are qualitatively explained. The Ti4+‐assisted Sc3+ diffusion would be utilizable in shortening the fabrication period of an optical‐damage‐resistant Ti‐diffused LiNbO3 waveguide doped with Sc3+, and some considerations for the fabrication are given.

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In this paper we report a chemical method named coordination reaction method to synthesize ZnO nanowire arreys. ZnO nanowires with the diameter about 80 nm were successfully fabricated in the channels of the porous anodic alumina (PAA) template by the above coordination reaction method. The microstructures of ZnO/PAA assembly were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the ZnO nanowires can be uniformly assembled into the nanochannels of PAA template. The growth mechanism of ZnO nanowires and the conditions of the coordination reaction are discussed. Photoluminescence (PL) measurement shows that the ZnO/PAA assembly system has a blue emission band caused by the various defects of ZnO.

We report a Ti:Er:LiNbO 3 strip waveguide with high diffusion-doped surface Er 3+ concentration. The waveguide was fabricated with a technological process in sequence of preparation of noncongruent, Li-deficient LiNbO 3 substrate by performing Li-poor vapor transport equilibration treatment on a congruent Z-cut LiNbO 3 plate, diffusion of 40-nm-thick Er metal film, and fabrication of 8-µm-wide Ti-diffused strip waveguide. The waveguide retains the LiNbO 3 phase and shows the waveguiding characteristics similar to the conventional Ti:LiNbO 3 waveguide. Secondary ion mass spectrometry study shows that the Er 3+ diffusion reservoir was exhausted and the profile is Gaussian with a surface concentration two times larger than that of the conventional Ti:Er:LiNbO 3 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.Index Terms-Ti:Er:LiNbO 3 waveguide, Er 3+ diffusiondoping, high Er 3+ concentration.

Diffusion-doping is an effective, practical method to improve material properties and widen material application. Here, we demonstrate a new physical phenomenon: diffusion control of an ion by another in LiNbO3 and LiTaO3 crystals. We exemplify Ti4+/Xn+ (Xn+ = Sc3+, Zr4+, Er3+) co-diffusion in the widely studied LiNbO3 and LiTaO3 crystals. Some Ti4+/Xn+-co-doped LiNbO3 and LiTaO3 plates were prepared by co-diffusion of stacked Ti-metal and Er-metal (Sc2O3 or ZrO2) films coated onto LiNbO3 or LiTaO3 substrates. The Ti4+/Xn+-co-diffusion characteristics were studied by secondary ion mass spectrometry. In the Xn+-only diffusion case, the Xn+ diffuses considerably slower than the Ti4+. In the Ti4+/Xn+ co-diffusion case, the faster Ti4+ controls the diffusion of the slower Xn+. The Xn+ diffusivity increases linearly with the initial Ti-metal thickness and the increase depends on the Xn+ species. The phenomenon is ascribed to the generation of additional defects induced by the diffusion of faster Ti4+ ions, which favors and assists the subsequent diffusion of slower Xn+ ion. For the diffusion system studied here, it can be utilized to substantially shorten device fabrication period, improve device performance and produce new materials.

Zr4+/Ti4+‐codoped LiNbO3 plates were prepared by local codiffusion of stacked ZrO2 and Ti metal films coated onto Z‐cut congruent LiNbO3 substrates in wet O2 at 1060°C. The metal and oxide films have different thicknesses and coating sequences. After diffusion, the Zr4+ doping effect on the refractive index of LiNbO3 and the Li2O out‐diffusion issue were studied by the prism coupling technique. The codiffusion characteristics of Zr4+ and Ti4+ were studied by secondary ion mass spectrometry. The results show that the Zr4+ doping has little contribution to the refractive index of the crystal. Li2O out‐diffusion is not measurable. In the Zr4+‐only diffusion case, the diffusivity of Zr4+ is four times smaller than that of Ti4+. In the Zr4+/Ti4+ codiffusion case, the Ti4+ codiffusion assists the Zr4+ diffusion. The Zr4+ diffusivity increases linearly by two more times with the increase in initial Ti film thickness from 0 to 200 nm. On the other hand, the Zr4+ affects the Ti4+ diffusion little. Neither the ZrO2 film thickness nor the coating sequence of Ti metal and ZrO2 oxide films influences the diffusivity of the two ions. All the codiffusion characteristics are explained. A Zr4+/Ti4+ codiffusion model is suggested that consists of two independent diffusion equations with a Zr4+ diffusivity dependent of Ti4+ concentration and a constant Ti4+ diffusivity. In addition, the existence of a waveguide in the Zr4+/Ti4+‐codoped layer is verified experimentally, and the optical‐damage‐resistant feature of the waveguide is verified by two‐beam hologram recording experimental results.

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