Plasmonic Antennas for Directional Sorting of Fluorescence Emission

• Published in: Nano letters 2011-06, Vol.11 (6), p.2400-2406
• Main Authors: Aouani, Heykel, Mahboub, Oussama, Devaux, Eloïse, Rigneault, Hervé, Ebbesen, Thomas W, Wenger, Jérôme
• Format: Article
• Language: English
• Subjects: Applied sciences; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Exact sciences and technology; Fluorescence; Gold - chemistry; Materials science; Molecular electronics, nanoelectronics; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nanostructures - chemistry; Optics; Particle Size; Physics; Quantum dots; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Solutions; Surface and interface electron states; Surface Properties; Water - chemistry
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl200772d

Spontaneous emission of fluorescent molecules or quantum dots is radiated along all directions when emitters are diluted in a liquid solution, which severely limits the amount of collected light. Besides, the emission direction does not carry any useful information and cannot be used to sort different molecules. To go beyond these limits, optical antennas have been recently introduced as conceptual tools to control the radiation properties for nanoemitters fixed on a substrate. Despite intense recent research, controlling the luminescence directivity remains a challenge for emitters with random positions and orientations, which is a key for several biomolecular screening applications. Here, we present full directional control of the fluorescence emission from molecules in water solution by an optical antenna made of a nanoaperture surrounded by a periodic set of shallow grooves in a gold film. For each emission wavelength, the fluorescence beam can be directed along a specific direction with a given angular width, hereby realizing a micrometer-size dispersive antenna. We demonstrate the fluorescence beaming results from an interference phenomenon and provide physical optics guidelines to control the fluorescence directivity by tuning the groove–nanoaperture distance. This photon-sorting capability provides a new approach for high-sensitivity screening of molecular species in solution.