Diluted melt proton exchange slab waveguides in LiNbO3: A new fabrication and characterization method.

A method of dilute-melt proton exchange employing a mixture of glycerol and KHSO4 with lithium benzoate added is used to fabricate planar waveguides in c-cut LiNbO3. With this exchange melt system the waveguide refractive index profiles can be fabricated with a high degree of reproducibility. In contrast with the traditional dilute-melt method, which uses benzoic acid and lithium benzoate, the need for seeled containers during the exchange process can be avoided when the glycerol, KHSO4 and lithium benzoate system is used for the exchange process. A new characterization method for determining the waveguide refractive index profile from the measured mode indices is introduced. The main advantage of this characterization method compared with other methods is that it also applies to single-mode waveguides. Using the new characterization method we investigate in detail the relation between waveguide refractive index change and composition of this glycerol, KHSO4 and lithium benzoate exchange melt system.