DNA-Templated Ultracompact Optical Antennas for Unidirectional Single-Molecule Emission

Abstract

Optical antennas are nanostructures designed to manipulate light–matter interactions by interfacing propagating light with localized optical fields. In recent years, numerous devices have been realized to efficiently tailor the absorption and/or emission rates of fluorophores. By contrast, modifying the spatial characteristics of their radiation fields remains challenging. Successful phased array nanoantenna designs have required the organization of several elements over a footprint comparable to the operating wavelength. Here, we report unidirectional emission of a single fluorophore using an ultracompact optical antenna. The design consists of two side-by-side gold nanorods self-assembled via DNA origami, which also controls the positioning of the single-fluorophore. Our results show that when a single fluorescent molecule is positioned at the tip of one nanorod and emits at a frequency capable of driving the antenna in the antiphase mode, unidirectional emission with a forward to backward ratio of up to 9.9 dB can be achieved.

Optical Ultracompact Directional Antennas Based on a Dimer Nanorod Structure

“…We associate this effect to the dark character of the antiphase mode that governs the response of the NRDA under this particular excitation. The spectral dependence of both the F/B ratio and the radiation efficiency, explain why in the experimental conditions [38] the bandpass filter and fluorescence band of the nanoemitter are matched with the antiphase mode of the NRDA. Otherwise, the maximum directionality would be reduced (see Figure S4).…”

“…Recently, we have realized experimentally, for the first time, the directional ultracompact antenna design originally proposed by Pakizeh and Käll [38]. Here, we present a numerical study of the performance of these antennas using Finite Element Method (FEM) simulations on gold nanorods (AuNRs) of sizes and shapes in accordance with our experimental samples.…”

“…As will be discussed later, the For the initial FEM far-field simulations, we choose AuNRs with commercially available sizes and similar to the experiments in Ref. [38]: 40 nm diameter (2R), 68 nm length (L) and ideal semi-sphere caps. Distances gap1 and gap2 are set to 5 nm.…”

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

“…Nanoemitters transmit photons in all directions since the momentum and position of photons cannot be simultaneously determined due to Heisenberg’s uncertainty principle. This leads to one of fundamental challenges in nanophotonics, how to confine the radiation of a nanoemitter into a desired direction and improve its coupling efficiency in miniaturized photonic devices, such as light emission devices, , single photon sources , and bio/chem-sensors. , To address the above challenge, researchers borrowed the idea of an antenna in the radio frequency − and developed a variety of optical antennas to control the optical properties of nanoemitters. , Particularly, by placing a nanoemitter at the feed point of an optical antenna, one can direct its emission into predefined directions with a high efficiency. ,− …”

DNA Self-Assembly of Single Molecules with Deterministic Position and Orientation

“…In addition to a high flexibility of geometric designs, DNA origami also serves as a nanometric breadboard to accommodate nanoparticles, biomolecules, and small molecules with positional and stoichiometric control. − Naturally, such a level of fine nanofabrication is finding application in many different areas, which include nanoelectronics, , drug delivery, sensing with nanopores, , and enhanced catalysis among others. Nanophotonics has been a particularly fertile field of application for DNA origami, as they were used to organize metallic nanoparticles and optically active molecules at the nanoscale, enabling nanodevices that present enhanced fluorescence, − single-molecule SERS, − artificial light harvesting, − plasmon assisted FRET, , multichromophoric FRET, − energy transfer from molecules to metal films or graphene, , molecular emission directivity, − and strong coupling at room temperature. , …”