## Abstract

The impact of third-order nonlinearities including self-phase modulation and two-photon absorption on the efficiency of the second-harmonic generation is numerically investigated using the split-step Fourier method in phase-matched Bragg reflection waveguides. Also using the same technique, the adverse effects of group velocity mismatch and group velocity dispersion of the interacting frequencies on the efficiency of the nonlinear process are examined and contrasted for optimal sample design. Using an optimized structure, we report efficient femtosecond second-harmonic generation in monolithic AlGaAs Bragg reflection waveguides for a type II nonlinear interaction. For a 190 fs pulsed pump around 1555 nm with an average power of 3.3 mW, a peak second-harmonic power of $25.5\text{\hspace{0.17em}}\mu \text{W}$ is measured in a sample with a length of 1.1 mm. The normalized conversion efficiency of the process is estimated to be $2.0\times {10}^{4}\mathrm{\%}\text{\hspace{0.17em}}{\text{W}}^{-1}\text{\hspace{0.17em}}{\text{cm}}^{-2}$. Pump depletion is clearly observed when operating at the phase-matching wavelength.

© 2010 Optical Society of America

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