We demonstrate absorber-free passive and hybrid mode-locking at sub-GHz repetition rates, using a hybrid integrated extended cavity diode laser operating near 1550 nm. The laser is based on InP as a gain medium and a Si3N4 waveguide feedback circuit. Absorber-free Fourier domain mode-locking with ≈15 comb lines at around 0.2 mW total power is achieved with repetition rates around 500 MHz, using three highly frequency-selective micro-ring resonators that extend the on-chip cavity length to 0.6 m. To stabilize the r…

We demonstrate absorber-free passive and hybrid mode-locking at sub-GHz repetition rates, using a hybrid integrated extended cavity diode laser operating near 1550 nm. The laser is based on InP as a gain medium and a Si3N4 waveguide feedback circuit. Absorber-free Fourier domain mode-locking with ≈15 comb lines at around 0.2 mW total power is achieved with repetition rates around 500 MHz, using three highly frequency-selective micro-ring resonators that extend the on-chip cavity length to 0.6 m. To stabilize the r…

Optical frequency combs based on broadband-gain bulk lasers, due to the low intrinsic linewidth and sub-GHz repetition rates, have gained tremendous interest for applications such as high-resolution spectroscopy, dual-comb spectroscopy or LIDAR. However, susceptibility to mechanical and acoustic perturbations, the complexity of optical pumping and the larger physical size of these lasers has motivated research toward chip-based integrated extended cavity diode lasers with low-loss Si₃N₄ waveg…

Diode lasers with low-loss dielectric feedback circuits based on hybrid integration are attractive because they are compact, can be efficiently driven via an electric current, and can be seamlessly integrated with advanced waveguide circuits. A central motivation to investigate these lasers is that they offer a significantly increased cavity photon lifetime, which has enabled single-frequency lasers with an extremely narrow intrinsic (Schawlow-Townes) linewidth of the laser frequency. In this thesis, we extend thi…

We demonstrate the first on-chip laser frequency comb based on hybrid integration with low-loss Si3N4 waveguide circuits. The laser comprises an InP diode amplifier of which a small fraction is reverse biased for passive locking, while a Si3N4 feedback waveguide extends the optical cavity to a roundtrip length of 15 cm. The generated comb densely covers a 25 nm broad spectrum, at a 3 dB level, with more than 1600 comb-lines at 2 GHz spacing. With such properties, hybrid integrated diode lasers show great promise f…