Mid-infrared silicon photonic lasers based on GeSn slab waveguide on silicon

GeSn alloy has emerged as an attractive active material for Si-based mid-infrared (MIR) lasers due to its direct bandgap nature at higher Sn concentrations. Here, we report on an optically-pumped GeSn MIR lasers based on planar slab waveguide with a top Si ridge structure. The inclusion of 10% Sn transforms the GeSn active layer into a direct bandgap material. The Si ridge structure ensures appropriate optical confinements with reduced scattering loss from the waveguide sidewall. Lasing action was achieved under optical pumping with a low threshold of 60.85 kW/cm² and an emission wavelength of 2238 nm at T = 40 K. Lasing action was also observed up to T = 90 K with a threshold of 170 kW/cm².