Abstract
Silicon (Si) photonics has emerged as one of the most promising technologies for the realization of ultra-dense photonic chips thanks to the mature Si industry, the large wafer size and the optical properties of Si and related materials. One of the major remaining challenges is the integration of high-performance light sources on Si. In particular, III-V semiconductor lasers are very efficient and their monolithic integration on Si, i.e. direct integration via epitaxy, is considered the most promising route to low-cost and large-scale fabrication of Si photonic chips. Among the various applications of Si photonics, optical sensing in the mid-IR is in high demand for societal, environmental or medical applications, among others. GaSb-based lasers have emerged as a technology capable of covering the mid-IR wavelength range. Therefore, the objective of my thesis is to integrate GaSb-based diode lasers on Si photonic integrated circuits (PICs). To this aim, I first investigated the degradation of laser performance caused by threading dislocations arising from the III-V-on-Si epitaxial growth. I then demonstrated the fabrication of these lasers on a Si PIC with similar performance to that of discrete lasers on Si. In addition, light coupling between the lasers and SiN-based waveguides was demonstrated. Finally, I investigated alternative approaches to increase the coupling efficiency. I developed the fabrication process of a new promising approach which paves the way for further investigations aimed at achieving high coupling efficiencies. Altogether, these results represent a significant step towards the monolithic integration of lasers on Si PICs for cost-effective and compact mid-IR sensors.