Fig. 6: Linewidth and side mode suppression ratio (SMSR) of the locked-state laser.

a Linewidth measurement setup. b Measured linewidth of 9.1 MHz limited by the resolution of the scanning Fabry–Perot (FP) interferometer. c Calculated fundamental linewidth versus loaded quality factor (QL) for 0.4 mW output power. About two orders of magnitude improvement can be achieved with higher QL of the microresonator and improved coupling between the Interband Cascade Laser (ICL) and the silicon chip. d Measured SMSR of 25 dB. The FP interferometer resonance is scanned over one free-spectral range (FSR) with a piezoelectric controller.