Quasi phase matching in GaAs-AlAs superlattice waveguides through bandgap tuning by use of quantum-well intermixing

We report the observation of second-harmonic generation by type I quasi pha se matching in a GaAs-AlAs superlattice waveguide. Quasi phase matching was achieved through modulation of the nonlinear coefficient chi(alpha y)((2)) which we realized by periodically tuning the superlattice handgap. Second- harmonic generation was demonstrated for fundamental wavelengths from 1480 to 1520 nm, from the third-order gratings with periods from 10.5 to 12.4 mu m. The second-harmonic signal spectra demonstrated narrowing owing to the finite bandwidth of the quasi-phase-matching grating. An average power of s imilar to 110 nW was obtained for the second harmonic by use of an average launched pump power of less than or equal to 2.3 mW. (C) 2000 Optical Socie ty of America.