Enhanced and directional molecular fluorescence in nanoaperture antennas

Controlling the fluorescence emission from nanoscale quantum emitters such as single molecules is a key element for a wide range of applications, from efficient analytical sensing to quantum information processing. Enhancing the fluorescence intensity and narrowing the emission directivity are both essential features to achieve a full control of fluorescence, yet this is rarely obtained simultaneously with optical nanoantennas. We report that gold nanoapertures surrounded by periodic corrugations transform standard molecules into bright unidirectional fluorescence sources [1]. We obtain enhancement factors of the fluorescence rate per molecule up to 75 fold simultaneously with a directional emission of the fluorescence into a narrow angular cone into a cone of ±15° in the direction normal to the sample plane. The bright emission and narrow directionality enable the detection of single molecules with a low numerical aperture objective, and improve the effectiveness of fluorescence-based applications. We thoroughly quantify the increased light-matter coupling as well as the radiation pattern intensity. The present demonstration is of high relevance for the development of advanced single molecule sensing, bright single-photon sources for quantum information processing, and light emitting devices. Reference [1] H. Aouani, O. Mahboub, N. Bonod, E. Devaux, E. Popov , H. Rigneault, T.W. Ebbesen, J. Wenger, Nano Letters 11, 637-644 (2011).