Proton exchange in Y-cut LiNbO3

In the present work, planar waveguides in Y-cut LiNbO3 were obtained using modified proton exchange (PE) conditions of: PE and subsequent annealing (A PE), PE in buffered melts (BMPE), APE followed by PE (APE + PE), and PE in vapours (VPE). Benzoic acid was used as the proton source in the PE, BMPE, and (APE + PE) experiments. Cinnamic acid was used for obtaining VPE-wavega ides. The main aim was to prevent surface damage of Y-cut crystals due to t he strains introduced by proton exchange. The investigations performed show ed that the surface etching is probably due to lattice deformation anisotro py leading to higher strains in PE Y-cut samples. Most encouraging results were observed, when an optimized (APE+PE)-procedure was used for waveguide formation. This method is very attractive for the fast preparation of deep high-index and low-loss waveguides in Y-cut LiNbO3. This procedure allows p assive and active elements to be produced in one and the same Y-cut substra te of LiNbO3. Similar preliminary results were obtained under VPE condition s. (C) 2001 Elsevier Science Ltd. All rights reserved.