Loss mechanisms and hybrid modes in high-δne proton-exchanged planar waveguides

We present the influence of temperature and melt acidity on the crystalline and optical quality of high-δn proton-exchanged waveguides fabricated in LiNbO3. Correlation with Rutherford backscattering and double-crystal x-ray diffraction experiments gives a physical basis for the choice of fabrication parameters that permit the realization of high-δne, low-loss planar waveguides. We pay special interest to the influence of strain-induced biaxiality in the guiding exchanged layers.