CERENKOV CONFIGURATION SECOND-HARMONIC GENERATION IN PROTON-EXCHANGED LITHIUM-NIOBATE GUIDES

We present a theoretical and experimental study of second harmonic generation using the Cerenkov configuration with proton-exchanged lithium niobate guides. The analytic solution of the problem for the case of planar step-index guides permits us to identify the essential role played by the discontinuity of the nonlinear polarization at the guide substrate interface. This leads to the prediction of an increasing conversion efficiency for decreasing values of guide nonlinearity. We show that the experimental results are consistent with a reduction of 50 to 70% of the value of the nonlinear coefficient in unannealed waveguides fabricated in slightly diluted or pure benzoic acid. The results presented enable the optimization of guide design for efficient second harmonic generation in the Cerenkov configuration. © 1990 IEEE