Directional Lasing in Coupled InP Microring/Nanowire Systems

The realization of on-chip microlasers with out-of-plane, controllable emission direction has been one of the core research themes in modern photonics. Traditional approaches for directional light scattering, including plasmonic nanoantennas and passive dielectric metasurfaces, are not suitable for on-chip integration due to potential metallic contamination and reliance on external light sources. Meanwhile, achieving directional emission in active III-V microcavity lasers remains challenging due to geometrical symmetry and large free-space coupling losses. Here, a novel approach is presented to realize directional lasing in an all-dielectric, bottom-up grown material system by coupling the laser emission from an InP microring cavity into a vertical nanowire at the ring center, which function as the photon source and directional antenna in the system, respectively. Efficient optical coupling is facilitated by enhanced light scattering at specific sidewall facets of the microring cavity, which can be engineered deterministically during epitaxial growth. Through Fourier imaging, out-of-plane laser emission with antenna-like far-field directivity in the coupled system is demonstrated. Furthermore, the emission directivity and side mode suppression in the coupled system can be improved significantly by tuning the geometric parameters of the system. The way for low power consumption, on-chip microlasers with tunable emission directionality is paved here.