HIGH-INDEX PROTON-EXCHANGED WAVE-GUIDES IN Z-CUT LINBO3 WITH UNDEGRADED NONLINEAR-OPTICAL COEFFICIENTS

A method is described for producing high quality optical waveguides on Z-cut LiNbO3 substrates by proton exchange in pure benzoic acid vapor . Either alpha- or beta-phase guides are obtained by varying the excha nge temperature (within the 250-375 degrees C range) and/or the treatm ent duration (between 15 min and 24 h). The method presents definitive advantages with regards to common immersion methods. For both alpha- and beta-phase guides the d(33) nonlinear optical coefficient is 90% o f the substrate value, and their optical losses are below 0.35 dB/cm. This is the first report on beta-phase guides with almost undegraded n onlinear optical coefficients. (C) 1997 American Institute of Physics.