Lasing in Group-IV Materials

Silicon photonics in the near-IR, up to 1.6 µm, is already one of key technologies in optical data communications, particularly short range. It also is being prospected for applications in quantum computing, artificial intelligence, optical signal processing, where complex photonic integration is to be combined with a large-volume fabrication. However, silicon photonics does not yet cover a large portion of applications in the mid-IR. In the wavelength range of 2–5 µm, environmental sensing, life sensing and security, all rely on optical signatures of molecular vibrations to identify complex individual chemical species. The markets for such analysis are huge and constantly growing, with a push for sensitivity, specificity, compactness, low-power operation and low cost. An all-group-IV, CMOS-compatible mid-IR integrated photonic platform would be a key enabler in this wavelength range. As for other wavelengths, such a platform should be complete with low-loss guided interconnects, detectors, eventually modulators, and most important an efficient and integrated light sources. This chapter reviews the recent developments of mid-IR silicon-compatible optically and electrically pumped lasers, light emitting diodes and photodetectors based on Ge, GeSn and SiGeSn alloys. It contains insights into the fundamentals of these developments, including bandstructure modelling, material growth and processing techniques.