Strategies for integration of lasers on silicon

There is a need for closer integration of lasers with silicon electronics in order to realize low-cost, energy-efficient transceivers in high-bandwidth short-reach interconnects for use in data centres, upcoming supercomputer architectures and in fibre-to-the-home applications. As silicon is an inefficient light emitter, it is necessary to integrate a direct bandgap material onto a suitable platform in order to provide the light signal. Powerful photonic integrated circuits can then be realized based on state-of-the-art CMOS wafers or on silicon-on-insulator platforms. We review the different approaches to large-scale integration of light sources with these platforms covering monolithic integration, wafer bonding and epitaxial layer transfer. Transfer printing is demonstrated to be a very effective strategy being scalable and, in conjunction with etched facet reflectors, capable of lithographic alignment in a planar fabrication process. Here, we demonstrate that with a substrate temperature of 60 °C with 100 mA drive current and a voltage of 2.1 V, a 390m long laser on a silicon substrate has a total power of >40 mW in continuous wave operation. This technology can also be used to provide the light source for plasmonic transducers required in heat assisted magnetic recording.