Design of an On-chip Mid-Infrared Erbium-Doped Laser

Erbium-doped waveguide-integrated lasers (EDWLs) play an increasingly important role in optical interconnects, optical communication, and biochemical sensing, due to their advantages of tunable spectral bandwidths, narrow linewidths, and large output powers. However, compared with the near-infrared (near-IR) band, the study of mid-infrared (mid-IR) EDWLs is still in its infancy. In this paper, we theoretically studied an EDWL at a wavelength of 3.6 I,tm. The model is based on a mid-IR suspended membrane silicon waveguide microring resonator integrated with an Erbium-doped chalcogenide glass thin layer. The designed laser could be fabricated with the combination of a CMOS-compatible silicon chip and Erbium-doped chalcogenide glass deposition through a post-fabrication process, making it be possible for high-volume and low-cost fabrication. We numerically calculated output characteristics of the laser by solving rate equations and a beam propagation equation. Specifically, after optimizing coupling coefficients of the resonator, the output power of the laser can reach 0.25 mu W. To further increase the laser slope efficiency, we designed a vertical Fabry-Perot cavity to increase the pump power intensity. Simulated results showed that the laser slope efficiency could be improved by a factor of six. Our study is expected to open an avenue to develop on-chip mid-IR lasers for exploring intriguing on-chip mid-IR applications in biochemical sensing, LiDAR, and nonlinear optics.