质子交换MgO:LiNbO3波导的双层结构

本文报导MgO:LiN_bO₃质子交换波导X射线双晶衍射和红外吸收的实验结果。这些结果表明质子交换波导由浅表面层和深表面层构成。浅表面层是一个连续应变层,有着大量随机排列的O—H—O形式的缔合OH^-基团。深表面层是一个均匀应变层,其内H⁺以自由OH^-基团形式出现。质子交换波导折射串不稳定性与双层结构中的结构驰豫密切相关。通过对质子交换过程的分析,提出两条避免双层结构的途径,其一为降低交换剂中的H⁺浓度,另一条是采用有限源工艺。

DOUBLE-LAYER STRUCTURE OF MgO: LiNbO_3 PROTON-EXCHANGED WAVEGUIDES

The experimental results of X-ray double crystal diffraction and IR absorption of MgO:LiNbO3 proton-exchanged waveguides are reported in this paper. It is found that proton-exchanged waveguides consist of a shallow surface layer and a deep surface layer. The shallow surface layer is a continuously strained layer, in which there are many associ-ated OH- groups randomly oriented in an O- H - O form. The deep surface layer is an uniformly strained layer, where H+ appears as a free OH- group. Refractive index instabi-lity of proton-exchanged waveguides is closely related to structure relaxation of the double-layer structure. On the basis of analysing the proton-exchange process, two ways to avoid the duble-layer structure are proposed: by reducing the H+ concentration in exchange agents and by using finite-source technique.