Measurement of Modulational Instability Gain of Second-Order Nonlinear Optical Eigenmodes in a One-Dimensional System

Abstract
We have investigated the amplification of a spatially periodic perturbation applied to a wide fundamental beam launched near phase matching for second-harmonic generation in a lithium niobate film waveguide. We measured the gain coefficient for the modulational instability of quadratic eigenmodes as a function of periodicity, intensity, and wave-vector mismatch. Excellent agreement with theory was obtained.