Heterogeneous quantum dot lasers on low-confinement silicon nitride with reduced-bending architecture.

Low-confinement silicon nitride (SiN) waveguides offer ultra-low losses but require wide bend radii to avoid radiative losses. To realize the benefits of silicon nitride in a heterogeneous laser while maintaining a small footprint, we employ metal-coated etched facets and transversely coupled Fabry-Perot resonators as mirrors. Heterogeneous quantum dot lasers are fabricated using an on-chip facet plus adiabatic taper coupler, and Fabry-Perot cavities are defined by metal mirrors and post-grating-distributed Bragg reflectors (DBRs). Threshold current densities below 250 A/cm are observed, and a power >15 mW is measured in an integrating sphere. A laser linewidth of <5 MHz is measured by tuning two lasers to about 50 MHz apart and measuring their beatnote on a photodiode. The total device footprint is <1 mm.