Room-Temperature Low-Threshold Plasmonic Nanolaser through Mode-Tailoring at Communication Wavelengths

Plasmonic nanolasers have shown unique potential for on-chip optical interconnects at optical communication wavelengths because of their ultra-small physical volumes beyond the diffraction limit. However, the high threshold and associated power consumption are key remaining challenges due to the long-recognized intrinsic plasmonic absorption and extrinsic losses related to the inevitable fabrication imperfections and the resulting rough surfaces or interfaces. This article demonstrates a new threshold-reduction strategy in a silver-cup plasmonic nanolaser by selectively confining plasmonic modes at the high-quality naturally cleaved surfaces at the bottom, while avoiding the rough etched surfaces of the sidewall. Through size control and modal design, lasing preferentially occurs via the bottom whispering gallery plasmonic mode with a large quality factor, small modal volume, and robust performance largely immune to fabrication imperfections. The nanolaser has a subwavelength volume of 0.02 lambda(3) near lambda = 1.55 mu m with a record-low threshold of 20.1 kW cm(-2) for a near-infrared plasmonic nanolaser at room temperature under optical pumping. Importantly, the laser becomes the first near-infrared plasmonic nanolaser to meet the power-consumption requirement of less than 10 fJ bit(-1), providing one of the rarely available on-chip sources with a small footprint and low power consumption for the photonic integrated circuits.