Zr 4+ /Ti 4+ Codiffusion Characteristics in Lithium Niobate

Zr 4+ /Ti 4+ ‐codoped LiNbO 3 plates were prepared by local codiffusion of stacked ZrO 2 and Ti metal films coated onto Z‐cut congruent LiNbO 3 substrates in wet O 2 at 1060°C. The metal and oxide films have different thicknesses and coating sequences. After diffusion, the Zr 4+ doping effect on the refractive index of LiNbO 3 and the Li 2 O out‐diffusion issue were studied by the prism coupling technique. The codiffusion characteristics of Zr 4+ and Ti 4+ were studied by secondary ion mass spectrometry. The results show that the Zr 4+ doping has little contribution to the refractive index of the crystal. Li 2 O out‐diffusion is not measurable. In the Zr 4+ ‐only diffusion case, the diffusivity of Zr 4+ is four times smaller than that of Ti 4+ . In the Zr 4+ /Ti 4+ codiffusion case, the Ti 4+ codiffusion assists the Zr 4+ diffusion. The Zr 4+ 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 Zr 4+ affects the Ti 4+ diffusion little. Neither the ZrO 2 film thickness nor the coating sequence of Ti metal and ZrO 2 oxide films influences the diffusivity of the two ions. All the codiffusion characteristics are explained. A Zr 4+ /Ti 4+ codiffusion model is suggested that consists of two independent diffusion equations with a Zr 4+ diffusivity dependent of Ti 4+ concentration and a constant Ti 4+ diffusivity. In addition, the existence of a waveguide in the Zr 4+ /Ti 4+ ‐codoped layer is verified experimentally, and the optical‐damage‐resistant feature of the waveguide is verified by two‐beam hologram recording experimental results.