Abstract
Silicon (Si) photonics represents the most promiising platform for the development of Photonic Integrated Circuits (PICs). Among the various applications addressed by Si PICs, the use of sensor grids/arrays is of particular interest. PICs sensors exploiting the mid-infrared spectral range (2-20 µm) are of great importance, as several molecules exhibit their fingerprint absorption lines within this wavelength window. Although, Si devices with excellent performance have been widely demonstrated, Si lacks light sources. III-V semiconductors, on the other hand, are very efficient materials for coherent light emission. The major remaining challenge is to achieve an efficient integration between Si PICs and III-V lasers. Among the different integration approaches proposed in literature, the one based on direct integration by epitaxy is considered as the “holy grail” for cost-effective and massively scalable on-chip light sources. The main objective of my thesis is to unlock this scenario by numerically and experimentally demonstrating the optical coupling between a GaSb-based diode laser monolithically integrated on a patterned Si substrate and SiN waveguides. To this aim, I first numerically investigated the optical coupling behaviour between a GaSb-based laser diode and a SiN waveguide in a butt-coupled configuration, followed by a study of potential alternative coupling geometries. The optical coupling between the laser and the passive SiN waveguide was then experimentally demonstrated. Finally, I explored strategies to further improve the optical coupling and developed new promising approaches for a robust optimization of the coupling efficiency. Altogether, this work paves the way to fully monolithically integrated Si photonic chips.