Mid-Infrared Emission Dynamics of InAs Nanowire Lasers

Picosecond mid-infrared (MIR) emissions from wurtzite indium arsenide (InAs) nanowire lasers were observed with time-resolved emission measurements based on a wavelength up-conversion technique. The nanowires exhibited an abrupt increase in the emission intensity at a pump fluence threshold of 53 μJ cm^-2/pulse. Below the threshold, the MIR emissions were characterized by a broad spectrum with a center wavelength of 2.6 μm and an exponential decay that was attributed to spontaneous emission dominated by nonradiative surface recombination. Above the threshold, intense and sharp spectral peaks appeared as a result of the optical cavity formed in the nanowire. Simultaneously, an ultrafast pulse as short as 8 ps was observed in the emission transient. A numerical simulation indicated that the intense picosecond MIR emission is stimulated emission from the InAs nanowire laser. These results contribute to the understanding of ultrafast emission dynamics of MIR nanolasers and show their potential for high-speed operation.