Heterostructure and Q-factor engineering for low-threshold and persistent nanowire lasing

Lasers: Record-breaking lasing nanowires Persistent short pulses of near-infrared laser light can be produced at record low thresholds using tiny nanowire lasers, suitable for small-scale optoelectronic devices, including optical computing chips. The technology has been developed and demonstrated by researchers in the UK, led by Patrick Parkinson at the University of Manchester. Their system is based on semiconducting nanowires composed of gallium arsenide phosphide and gallium arsenide. It combines both key functions of a laser in one material, as the gain medium that amplifies the light emission and the cavity medium for containing and manipulating the light. The researchers engineered the precise behavior of the nanowires to demonstrate highly optimized nano-lasing performance at room temperature lasing thresholds. Their work addresses and overcomes significant challenges that have been limiting developments in this promising field. 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 mu J cm(-2) pulse(-1)) for III-V nanowire lasers. Our findings demonstrate a highly promising new route towards continuously operating silicon-integrated nanolaser elements.