Second harmonic generation in GaAs/AlGaAs waveguides with femtosecond pulses near 1.55 /spl mu/m using modal phase matching technique

Modal phase matching (MPM) is a simple solution to the problem of phase velocity synchronism in nonlinear frequency conversion processes, but has been of limited interest because of the poor spatial overlap between the interacting modes. However, using a proper waveguide design, the overlap integral between the 3rd order mode and the fundamental can be optimised, resulting in a still appreciable effective nonlinearity. Using this technique, we report second harmonic generation in semiconductor waveguides with femtosecond fundamental pulses.