Nanowire-based opto-electronic devices including nanowire lasers, photodetectors and semiconductor optical amplifiers are disclosed. The devices include nanowires grown from single crystal and/or non-single surfaces. The semiconductor optical amplifiers include nanowire arrays that act as ballast lasers to amplify a signal carried by a signal waveguide. Embodiments of the nanowire lasers and photodetectors include horizontal and vertical nanowires that can provide different polarizations.