"This proposal is concerned with optically-injected nanostructure lasers, including quantum-dot and quantum-dash semiconductor lasers and the potentials of these devices for Ultra-High Frequency applications, including Terahertz (THz) technologies. In particular, attention will be focused on long-wavelength devices, emitting at the very important telecom wavelengths of 1310 and 1550nm. The aim of this proposal is to analyze experimentally and in theory the effect of optical injection in several nanostructure lasers, including Fabry-Perot, Distributed-Feedback (DFB) and multisection DFB devices with quantum dot and quantum dash active regions. The investigations will include the analysis of the injection locking properties and the mapping of the different regions of nonlinear dynamics when the devices are subject to weak optical injection. In addition, the enhancement of the modulation bandwidth and resonance frequency when these devices are subject to high and ultra-high external optical injection will also be investigated throughout the Fellowship. The limits in the enhanced frequency response will be analyzed for different designed optically-injected nanostructure lasers and the prospects of these devices for use in Ultra-High Frequency applications will be explored. In particular, attention will be focused in pushing up the frequency response of these devices to the THz frequency range which has a wide variety of applications in very disparate fields, including communications, biology, medicine, security, sensing etc. Hence, the vision of this project will be the practical development of a Tuneable THz oscillator built directly from simple and compact photonic components such as nanostructure semiconductor lasers totally compatible with optical communications technologies."