1. Diffusivity of Er3+ into LiNbO3 as a function of stoichiometry.
- Author
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Zhang, De-Long, Hua, Ping-Rang, Yang, Qing-Zhong, Liu, Hong-Li, Cui, Yu-Ming, and Pun, E. Y. B.
- Subjects
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MASS (Physics) , *ANISOTROPY , *CRYSTALLOGRAPHY , *SEPARATION (Technology) , *SEMICONDUCTOR doping , *DIFFUSION , *WAVEGUIDES , *NOBLE gases - Abstract
Diffusivity of Er3+ into LiNbO3 crystal has been studied as a function of Li2O content and crystal orientation. The Li2O content in single-crystal LiNbO3 plates was adjusted by Li-rich vapor transport equilibration (VTE) technique. Five X-cut and five Z-cut congruent substrates were VTE treated at first at 1100 °C for different durations ranging from 6 to 74 h, and then were subjected to a special post-VTE anneal procedure at the same temperature for 60 h to obtain homogeneous Li2O content. The Li2O content was determined from the measured fundamental optical absorption edge. Its homogeneity is verified by measuring the optical absorption edge as a function of the crystal thickness. After the composition characterization, the substrates were coated with 45 nm thick Er film and annealed at 1130 °C for 40 h in argon atmosphere. The Er3+ profile was analyzed by secondary ion mass spectrometry. The results show that the Er3+ diffusivity decreases monoexponentially with the increase in the Li2O content in both cases of X- and Z-cut. As the Li2O content is increased from the congruent point (48.4 mol %) to the near-stoichiometric composition (∼49.9 mol %), the diffusivity decreases from 0.107 (0.072) to 0.017 (0.018) μm2/h for the Z (X)-cut substrate. The diffusion shows considerable anisotropy for the lower Li2O content and the diffusivity in a Z-cut substrate is larger. The anisotropy weakens gradually with the increase in the Li2O content, and the diffusivities in the X- and Z-cut substrates ultimately tend to a same value (∼0.02 μm2/h) at the Li-rich phase boundary. After the Er diffusion procedure, endface coupling experiment was carried out to check if a planar waveguide layer was formed near the Er-diffused surface due to the Li outdiffusion. The results show that the Li outdiffusion did not accompany the Er diffusion procedure. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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