Silicon Photonics is a new technology that allows to create photonic devices that use silicon as an optical medium, with the final goal of integrating photonic and electronic devices on the same silicon chip. Although various passive optical devices have been successfully demonstrated in the context of Silicon Photonics, the most important building block of an optical system, i.e. an efficient laser source, monolithically integrated on Si, is still missing. This is due to the fact that silicon is an indirect band-gap material. Nowadays, several technological solutions are available to overcome this problem. An overview of the state-of-the-art of the available techniques for laser integration on silicon is presented in the first part of this work.