STRUCTURE OF HIGH-INDEX PROTON-EXCHANGE LINBO3 WAVE-GUIDES WITH UNDEGRADED NONLINEAR-OPTICAL COEFFICIENTS

A structural study is presented on proton exchanged LiNbO3 waveguides prepared in benzoic acid vapor which, for z-cut substrates, were previ ously reported to simultaneously exhibit high index jump, very low los ses, and undegraded nonlinear optical coefficients. X-ray rocking curv es of z-cut guides show a unique, intense peak with the same bandwidth as the substrate peak, located at the kappa(2)-phase position of HxLi 1-xNbO3, as well as a small alpha-phase contribution. For x-cut guides only the beta(1)-phase peak is obtained, with a bandwidth about 60% g reater than the substrate peak. Distinctive features of kappa(2) and b eta(1) guides are also shown in micro-Raman spectra. (C) 1997 American Institute of Physics.