The last decade data-intensive technologies are increasingly emerging, mandated by the information-demanding society’s and industry’s needs. To that end, efficient structures for the massive storage and fast distribution of information are required. Data centres play a pivotal role on the global data traffic management, with their electrical interconnects being an efficiency restriction. Modern data centres can adapt to the big data and bandwidth challenges through their all-optical transformation incorporating fully integrated photonic transceivers. The low-cost high-volume infrastructure of the relatively mature silicon photonics field is gaining traction because of its nano-metric size and low-loss SOI devices. However, the material is lacking in light generation and is restricted in efficient O-band compact modulators. These limitations necessitate its integration with multi-material platforms, composed of quantum semiconductor micro-metric stacks. To surpass the coupling-restrictive size bottleneck, this thesis proposes the utilisation of the alternative silicon nitride (SiN) platform to enable an active-to-passive transition. Being low-temperature and grown in amorphous layers, silicon nitride can act as a bridging path between the thin SOI and the thick active quantum-layer components. The proof-of-concept scheme described in this thesis is demonstrated through the butt-coupling of a thick SOI layer to a N-rich SiN layer forming a passive O-band waveguide interconnection. A characterised transition of <0.5 dB coupling loss and <−16 dB back-reflection has been achieved. Moreover, the coupling strategy is extended for a SiN-integrated III/V dot-in-well O-band laser. A coupling loss of <1.7 dB for a device on GaAs has been measured, keeping a <−40 dB simulated back-reflection level. In addition, a SiN-integrated multiple SiGe quantum well O-band modulator is investigated, showing computationally a transition of <0.4 dB coupling loss and <−40 dB back-reflection. Furthermore, a SiGe-based effective index change potential of 4 × 10−3 is demonstrated by characterising electrically driven Mach-Zehnder devices. The proposed monolithic approach is envisaged to contribute to the data centres’ photonic transformation and boost further their information-management capacity.