Zr⁴⁺/Ti⁴⁺ Codiffusion Characteristics in Lithium Niobate

Abstract

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.

Unveiling the Defect Structure of Lithium Niobate with Nuclear Methods

“…For completeness, it should be mentioned, that also other elements, Sc [279] and Zr [280], which are candidates for waveguide formation were studied with regard to their diffusion properties using SIMS. Further, several studies focused on the co-diffusion of two elements: Zn/Ni [281], Zr/Ti [282,283], Sc/Ti [283] as well as for waveguide laser applications, the important Er/Ti [283,284].…”

New Trends in Lithium Niobate

“…For completeness, it should be mentioned, that also other elements, Sc [279] and Zr [280], which are candidates for waveguide formation were studied with regard to their diffusion properties using SIMS. Further, several studies focused on the co-diffusion of two elements: Zn/Ni [281], Zr/Ti [282,283], Sc/Ti [283] as well as for waveguide laser applications, the important Er/Ti [283,284].…”

Nonlinear diffusion model for annealed proton-exchanged waveguides in zirconium-doped lithium niobate

“…Furthermore, LiNbO 3 has been studied extensively over the last several decades, resulting in both the implementation of quasi-phasematching (QPM) [2] as well as the development of several waveguide-fabrication technologies. Among the latter are methods based on the indiffusion of protons [3] or transition metals [4,5] to form the waveguide core, mechanically defined guiding structures via etching or dicing [6], or hybrid approaches [7]. The goal of these methods is to significantly increase the small-signal conversion efficiency of nonlinear frequency conversion by confining the interacting waves to a small cross section over an appreciable distance much greater than their natural diffraction length.…”