Highly efficient light extraction and directional emission from large refractive-index materials with a planar Yagi-Uda antenna

Light emission is a basic process at the core of applications in optics and photonics, such as lighting, sensing and telecom. Despite extensive work on the design of light-matter interfaces, the outcoupling of electromagnetic radiation from nanoscale sources is still a challenge. Here, we show how a planar Yagi-Uda antenna based on thin-film optics can lead to more than 90% outcoupling efficiency and strong directional emission from materials with a large refractive index. Our findings are particularly relevant for semiconductor-based nanophotonic devices, which typically suffer from a large mismatch with respect to free-space and guided modes. (C) 2017 Optical Society of America