On-chip light sources for silicon photonics

Serving as the electrical to optical converter, the on-chip silicon light source is an indispensable component of silicon photonic technologies and has long been pursued. Here, we briefly review the history and recent progress of a few promising contenders for on-chip light sources in terms of operating wavelength, pump condition, power consumption, and fabrication process. Additionally, the performance of each contender is also assessed with respect to thermal stability, which is a crucial parameter to consider in complex optoelectronic integrated circuits (OEICs) and optical interconnections. Currently, III-V-based silicon (Si) lasers formed via bonding techniques demonstrate the best performance and display the best opportunity for commercial usage in the near future. However, in the long term, direct hetero-epitaxial growth of III-V materials on Si seems more promising for low-cost, high-yield fabrication. The demonstration of high-performance quantum dot (QD) lasers monolithically grown on Si strongly forecasts its feasibility and enormous potential for on-chip lasers. The superior temperature-insensitive characteristics of the QD laser promote this design in large-scale high-density OEICs. The Germanium (Ge)-on-Si laser is also competitive for large-scale monolithic integration in the future. Compared with a III-V-based Si laser, the biggest potential advantage of a Ge-on-Si laser lies in its material and processing compatibility with Si technology. Additionally, the versatility of Ge facilitates photon emission, modulation, and detection simultaneously with a simple process complexity and low cost.