This chapter reviews approaches used to design and prepare structures for both the 1.3–1.6 μm spectral window of low hydroxyl content optical fibres, and the 0.98–1.04 μm one for telecom and medical applications. In order to take full advantage of the peculiar optical properties of quantum dot (QD) nanostructures, their band structure must be engineered to optimize a few relevant parameters. Self-assembled semiconductor QDs have unique properties that make them extremely interesting for photonic devices with improved performances such as QD lasers. Such properties are intrinsic and are related to the zero-dimensional confinement of carriers in the structures. The chapter also demonstrates that how by a careful design of structures grown under well-defined conditions it is possible to cover the 0.98–1.04 μm and 1.3–1.6 μm windows with QD nanostructures based on GaAs substrates, a result that could open the path to the realization of QD photonic and optoelectronic devices for a wide range of applications.