Broadband Mode-Locked III-V/LiNbO₃ Microcomb Laser

The mode-locked lasers composed of a III-V gain chip and a LiNbO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>-on-insulator (LNOI) chip have attracted widespread attention due to their high integration and tunability [1], [2]. However, the spectral range is limited to around 5 nm. The spectrum can be broadened by exploring the Kerr effect in a ring resonator, but this requires precise dispersion engineering of the waveguide. In this work, we generate a broadband mode-locked microcomb covering a 27-nm spectral range by using the broadband gain of a reflective semiconductor optical amplifier (RSOA). The laser is output from the gain chip, which helps to decrease the coupling loss between the chip and the optical fiber, allowing the off-chip average power of the laser to reach up to 26 mW. The demonstration of such a broadband mode-locked microcomb laser highlights its significant potential for a variety of applications, including data communications, LiDAR, and spectroscopic sensing.