Heterogeneous Integration of Multi‐Band Mode‐Locked and Single‐Mode Lasers on an Extended Commercial SiN Platform

ABSTRACT

Integrated silicon nitride (SiN) waveguides offer ultra‐low propagation loss across a broad transparency window, enabling large‐scale photonic integrated circuits (PICs) for applications from LiDAR to quantum photonics. However, integrating lasers on SiN PICs remains challenging due to the large refractive‐index contrast between SiN and high‐index III–V gain materials. We address this by extending Ligentec's commercial bi‐layer SiN platform with a polycrystalline silicon (Poly‐Si) layer and demonstrate heterogeneous integration of GaAs‐ and InP‐based amplifiers via a scalable process called micro‐transfer printing. Multi‐section adiabatic tapers ensure efficient coupling from the SiN to Poly‐Si layer and onward to the printed III–V devices. In a single fabrication run, we realize a diverse set of lasers, including the first O‐band GaAs‐on‐SiN mode‐locked laser (5.1 GHz repetition rate, 5.4 ps pulse width), a C‐band mode‐locked laser delivering >1 mW optical power per output, and multiple single‐mode sources (ring‐filter and distributed Bragg reflector cavities) with side‐mode suppression ratio up to 51 dB and intrinsic linewidth down to 1 kHz. These results demonstrate how combining micro‐transfer printing with an extended SiN platform enables versatile, multi‐wavelength laser integration, establishing a practical route to complex light sources for advanced photonic systems.