Achieving High Stability of Dual-Wavelength U-Shaped Laser in the C-Band Using Optical Feedback

Dual-wavelength lasers are attractive for various fields such as terahertz generation and high-precision spectroscopy, particularly when exhibiting narrow-linewidth performance. This study focuses on linewidth measurements of a monolithically-integrated InP dual-wavelength laser emitting in the telecom C-band. Linewidths below 3 MHz are demonstrated for both lines, which reduce to values below 40 kHz after introducing optical feedback from both sides of the laser cavity. The device has a small form-factor and is made with mature technologies, and as such has direct applications in the aforementioned fields.