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. Electrically‐driven photonic crystal microlaser has been demonstrated, featuring continuous wave operation with an ultra‐low threshold of 10.2 µA at room temperature. This analysis shows that the temporal confinement of the photons in such laser cavities is dominated by the absorption of the p‐type doping used for electrical injection and also shows that the efficiency is limited by the leakage current.