质子交换LiTaO_3光波导特性及晶格常数变化

Lattice Constant Change and Characteristic of Proton-exchanged LiTaO_3 Waveguide Layer

采用气相质子交换方法，在Ｚ－切ＬｉＴａＯ３晶体表面制备平面光滑波导层。样品制备采用２４５℃苯甲酸气体，在 ＬｉＴａＯ３晶体在－Ｃ和＋Ｃ表面交换 ８～２０ 小时。质子交换层在 ＬｉＴａＯ３表面形成，并用棱镜耦合测量波导样品。然后在ＨＦ：ＨＮＯ３酸中用化学方法腐蚀波导层，并用电子显微镜观测光波导层与衬底界面的形貌。用Ｘ射线衍射法，测量ＬｉＴａＯ３质子交换光波层的晶格常数变化。用双晶Ｘ射线测量质子交换（ＰＥ）和退火质子交换（ＡＰＥ）波导层晶格常数的变化。样品的Ｘ射线衍射曲线表明，ＰＥ和ＡＰＥ波导晶格常数的变化不同。实验中，还测量了有无极畴反转ＬｉＴａＯ３晶格常数的改变。

Using benzoic acid gas, we fabricated proton-exchanged planar waveguide layer in z-cut LiTaO3 surface. 'The preparations of the samples are as follows: First, waveguides layer was fabricated in the - c and + c face of LiTaO3 substrates in benzoic acid gas at 245℃ for 8~20h. The proton-exchanged layers were formed in the face of LiTaO3. Then the samples of waveguide were measured by prism coupling method. After that, waveguide layer in the surface of LiTaO3 was etched in HF: HNO3 acid and then mea- susured by use of electronic microscope. Using chemical etch method, we observed waveguide layer and the shape and form of inner interface of waveguides. Using X-ray diffraction method, we measured the change of lattice constant of proton-exchanged waveguide. The double crystal X-ray diffraction rocking curves analysis was used to determine the lattice constants of the proton-exchanged (PE) and annealed proton-exchanged (APE) 1ayer. The X-ray diffrac- tion rocking curves of the sample show that the rate of the lattice constant changes of the PE and APE were different. The lattice constants of the LiTaO3 substrates without and with the domain-inverted slab struc- ture were measured. The experimentaI results were reported and discussed in detail.