Ultra-Stable Broadband Comb Laser with Tunable Free Spectral Range and Spectra

We present a novel near-infrared broadband, flat-top optical frequency comb spanning 1.6 THz. This comb is generated using an interband gain medium operated in an ultrafast gain recovery regime within a unidirectional ring cavity. The remarkable stability of our approach is evidenced by a 1 Hz RF linewidth. The injected RF signal not only governs the spectral bandwidth and free spectral range but also tailors the comb’s spectral shape—a feat achieved by simultaneously injecting multiple modulation tones. This advanced level of control opens promising avenues for applications in communication, sensing, and ranging, where precise and stable frequency lines are essential for performance and reliability.