Review of mid-infrared on-chip integrated photonics (Invited)

With the development of information technology, integrated photonics at telecom band has caught broad attention, made outstanding progress in the past few decades, and has also been commercialized in recent years. The development of integrated photonics at the telecom band has also inspired people to be interested in integrated photonics at the mid-infrared (Mid-IR) band (2-20 μm). Mid-IR has promising potential in applications such as space optical communications, thermal imaging, material detection, and analysis, which is of vital significance in national development, national security, and improvement of people ’s welfare. Utilizing semiconductor fabrication processes, a miniature Mid-IR optoelectronic system integrated on a chip has superior advantages in terms of the device ’s size, power consumption, and mass production compared to conventional solutions. Therefore, it is meaningful to develop chip-scale Mid-IR photonics. In this review, the representative works and breakthroughs of fundamental integrated devices at Mid-IR wavelength including modulators and detectors in recent years were reviewed and evaluated. The classification, performance matrics, parameters, and fabrication methods of different kinds of devices were discussed and compared comprehensively. Meanwhile, the developing progress, unsolved problems, and prospects of integrated Mid-IR devices were analyzed.