Packaged Long Cavity Hybrid III-V/Si₃N₄ Mode-Locked Laser With Improved Modulation Efficiency

Optical frequency combs are at the center of numerous applications such as LIDAR and RADAR systems, metrology, telecommunication, and spectroscopy. Among the different ways of frequency comb generation, integrated mode-locked lasers offer lower cost, smaller footprint, and easier system integration than their bulk counterparts. In this work, we demonstrate a III-V/ $\text{S}_{\mathrm {i3}}\text{N}_{4}$ hybrid integrated mode-locked laser developed for RADAR applications to fulfill the role of a frequency bank in the RF domain. Thanks to the low-loss in silicon nitride waveguides, we were able to design a cm-long cavity that enables low noise operation with a very low repetition rate of 364 MHz, which provides high precision when generating RF frequencies. In this letter, we demonstrate passive and harmonic mode locking, with an improved electrical modulation efficiency in the active chip.