DIRECT MEASUREMENT OF ORDINARY REFRACTIVE-INDEX OF PROTON EXCHANGED LINBO3 WAVE-GUIDES

A method for the direct measurement of ordinary refractive index n(o) of proton-exchanged LiNbO3 waveguides is proposed and demonstrated. Values of DELTA-n(o) are given for a variety of guides (X-cut, Y-cut, different lithium benzoate concentrations, annealed or unannealed). The relation DELTA-n(o) = 0.007 - 0.40-DELTA-n(e) holds for all DELTA-n(o) values, except for unannealed guides prepared in pure benzoic acid that show DELTA-n(o) relatively higher. The usefulness of the method for the experimental study of anisotropic guides presenting hybrid leaky modes is shown.