On-chip chalcogenide microresonators with low-threshold parametric oscillation

Chalcogenide glass (ChG) is an attractive material for highly efficient nonlinear photonics, which can cover an ultrabroadband wavelength window from the near-visible to the footprint infrared region. However, it remains a challenge to implement highly-efficient and low-threshold optical parametric processes in chip-scale ChG devices due to thermal and light-induced instabilities as well as a high-loss factor in ChG films. Here, we develop a systematic fabrication process for high-performance photonic-chip-integrated ChG devices, by which planar-integrated ChG microresonators with an intrinsic quality (Q) factor above 1 million are demonstrated. In particular, an in situ light-induced annealing method is introduced to overcome the longstanding instability underlying ChG film. In high-Q ChG microresonators, optical parametric oscillations with threshold power as low as 5.4 mW are demonstrated for the first time, to our best knowledge. Our results would contribute to efforts of making efficient and low-threshold optical microcombs not only in the near-infrared as presented but more promisingly in the midinfrared range.