Research progress of mid-infrared silicon-based modulators (Invited)

Silicon-based photonics is expected to be extended to the mid-infrared (MIR) wavelength, due to the low absorption of silicon (Si) material in the range of 1.1 μm to 8.5 μm. With the needs emergence of communication window expansion, gas molecular detection, infrared imaging and other applications, the development of silicon-based devices in the mid-infrared wavelength is imperative. Silicon-based modulator plays an important role in the research and development of silicon-based optoelectronic devices in MIR. It is an indispensable link in long wave optical communication system, and can be used in on-chip sensing system to improve the signal-to-noise ratio and realize optical switching. It is found that silicon and germanium materials have greater free carrier effect and thermal-optical effect in the MIR band than that in the near-infrared band (NIR). It is proved that silicon-based materials have unique advantages in the development of mid-infrared modulators. The development trend and research status of MIR silicon-based modulators were summarized. The working principle and latest research progress of electro-optic modulators and thermal-optic modulators based on silicon and germanium materials were introduced. Finally, the mid-infrared silicon-based modulators were summarized and prospected.