The nonlinear optical properties of gallium arsenide/aluminum arsenide superlattice-core waveguides at telecommunications wavelengths

This thesis examines the nonlinear optical properties of 14:14 GaAs/AlAs superlattice-core waveguides at wavelengths in the 1550 nm telecommunications range. The linear optical properties of as-grown superlattice show polarization dependencies that are attributed to the difference in the half-bandgap for TE and TM polarizations and the structural anisotropy of the superlattice. Two-photon absorption measurements in as-grown superlattice yielded polarization-dependent coefficients between 1.5 cm/W to 4.0 cm/W, which are larger than in bulk AlGaAs. Spectral broadening induced by self-phase modulation was observed to give nonlinear refraction coefficients n2 of 1.5 cm²/W to 5.5 cm²/W with TE modes having values as much as twice as large as the TM mode. The ratio of self- to cross-phase modulation between polarizations showed a polarization dependence. Intermixing superlattice resulted in a reduction in n2 by one order of magnitude. Figure of merit values show superlattice is a viable material for nonlinear optical devices.