Tunable single-mode chip-scale mid-infrared laser

Portable mid-infrared (mid-IR) spectroscopy and sensing applications require widely tunable, chip-scale, single-mode sources without sacrificing significant output power. However, no such lasers have been demonstrated beyond 3 mu m due to the challenge of building tunable, high quality-factor (Q) on-chip cavities. Here we demonstrate a tunable, single-mode mid-IR laser at 3.4 mu m using a tunable high-Q silicon microring cavity and a multi-mode Interband Cascade Laser. We achieve single-frequency lasing with 0.4 mW output power via self-injection locking and a wide tuning range of 54 nm with 3 dB output power variation. We further estimate an upper-bound effective linewidth of 9.1 MHz and a side mode suppression ratio of 25 dB from the locked laser using a scanning Fabry-Perot interferometer. Our laser platform based on a tunable high-Q microresonator can be expanded to higher wavelength quantum-cascade lasers and lead to the development of compact, high-performance mid-IR sensors for spectroscopic applications. The availability of integrated mid-infrared light sources is restricted by a lack of suitable materials and increasingly complicated fabrication requirements. Here, a single-mode silicon microresonator laser is demonstrated, who's emission in the mid-infrared can be tuned by integrated microheaters.

Automated summary

This study demonstrates a tunable, single-mode mid-IR laser at 3.4 μm using a tunable high-Q silicon microring cavity and a multi-mode Interband Cascade Laser. By utilizing self-injection locking, single-frequency lasing with 0.4 mW output power and a wide tuning range with high side mode suppression ratio were achieved.