Smart Magnetic Optical Antenna for Automatic Nanoalignment and Photon Beaming from Prepatterned Single Quantum Dot Nanospot.

We present a unidirectional dielectric optical antenna, which can be chemically synthesized and controlled by magnetic fields. By applying magnetic fields, we successfully aligned an optical antenna on a prepatterned quantum dot nanospot with accuracy better than 40 nm. It confined the fluorescence emission into a 16-degree wide beam and enhanced the signal by 11.8 times. Moreover, the position of the antenna, and consequently the beam direction, can be controlled by simply adjusting the direction of the magnetic fields. Theoretical analyses show that this magnetic alignment technique is stable and accurate, providing a new strategy for building high-performance tunable nanophotonic devices.