Electrically-Driven Photonic Crystal Lasers with Ultra-low Threshold

Light sources with ultra-low energy consumption and high performance are required to realize optical interconnects for on-chip communication. Photonic crystal (PhC) nanocavity lasers are one of the most promising candidates for this role. In this work, a continuous-wave PhC nanolaser with an ultra-low threshold current of 10.2 µA emitting at 1540 nm and operated at room temperature is demonstrated. The lasers are InP-based bonded on silicon (Si), and comprise a buried heterostructure active region and lateral p–i–n junction, feature CMOS-compatible drive voltage, and exhibit low self-heating. Carrier leakage is a fundamental limitation of the lateral pumping scheme that is identified as unwanted spontaneous emission from the InP p–i interface, limiting the injection efficiency to 3% which further decreases at higher current. The effect of fabrication disorder and p-doping absorption on the Q-factor is studied experimentally showing that p-doping limits the Q-factor to 8000, with a p-doping absorption coefficient of 120 cm⁻¹.