Using benzoic acid gas

we fabricated proton-exchanged planar waveguide layer in

z

-cut LiTaO

3

surface.'The preparations of the samples are as follows:First

waveguides layer was fabricated in the-c and+c face of LiTaO

3

substrates in benzoic acid gas at 245℃ for 8~20h.The proton-exchanged layers were formed in the face of LiTaO

3

.Then the samples of waveguide were measured by prism coupling method.After that

waveguide layer in the surface of LiTaO

3

was etched in HF:HNO

3

acid and then measusured 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 LiTaO

3

substrates without and with the domain-inverted slab struc-ture were measured.The experimentaI results were reported and discussed in detail.