Ultrafast tunable hybrid Yagi-Uda nanoantenna

We study radiation from Yagi-Uda nanoantennas composed of metal-dielectric core-shell nanoparticles. We have found an interesting operation regime in such nanoantennas determined by their hybrid nature. This regime rests on the excitation of the Van Hove singularity, supporting high values of directivity and Purcell factor within the same narrow frequency range. In this regime, a strong dynamical tuning of the emission pattern via electron-hole plasma photoexcitation by a femtosecond pumping can be achieved.