Nanooptics

Directing the emission of a quantum emitter into a specific direction is interesting but rather less explored due to the technically demanding fabrication of subwavelength antenna–emitter hybrid nanostructures. In particular, placing the emitter precisely in the correct location to drive the desired resonant mode of a nanoantenna is technically demanding because it requires sub-5-nm spatial precision and certain orientation control. Therefore, much effort has been put into developing deterministic, precise, high-throughput, and low-cost fabrication methods to address these challenges. The emerging DNA origami technique provides a unique solution and has been used to develop ultrasmall optical nanoantennas for unidirectional single-molecule emission. This rather research direction is gaining attention due to its potential applications in directional single-photon sources, optical biosensors, and integrated photonic chips. This paper gives a spotlight on the recent advances in DNA origami-assisted ultrasmall optical nanoantennas for directing single-molecule emission in a specific direction. The capability of the DNA origami technique to precisely position and assemble plasmonic nanoparticles and single quantum emitters into unidirectional transmitting optical nanoantennas is illustrated by highlighting representative recent works. In addition to the fabrication, the impact of origami and the mechanisms for unidirectional emission are also discussed.