Heterostructure and Q-factor Engineering for Low-threshold and Persistent Nanowire Lasing

Continuous room-temperature nanowire lasing from silicon-integrated optoelectronic elements requires careful optimisation of both the lasing cavity Q-factor and population inversion conditions. We apply time-gated optical interferometry to the lasing emission from high-quality GaAsP/GaAs quantum well nanowire laser structures, revealing high-Q factors of 1250±90 corresponding to end-facet reflectivities of R= 0.73±0.02. By using optimised direct-indirect band alignment in the active region, we demonstrate a well-refilling mechanism providing a quasi-four-level system leading to multi-nanosecond lasing and record low room-temperature lasing thresholds (~ 6 μJcm-2pulse-1) for III-V nanowire lasers. Our findings demonstrate a highly promising new route towards continuously operating silicon-integrated nanolaser elements.