Periodic arrays of plasmonic nanoantennas can enhance the directionality of light emission of nearby ﬂuorophores. Unfortunately, their narrow spectral bandwidth and the anisotropy of their optical resonances limit the use of these structures in applications such as solid state lighting. In this article, we study an alternative that is as effective at outcoupling light, yet broadband: Vogel’s golden spirals. These spirals are deterministic structures with an approximate circular symmetry and a Fourier transform that is much more broadband than that of periodic lattices. Their use as plasmonic antennas was first proposed by the group of Lucal dal Negro at Boston University.
Photoluminescence measurements show that the spirals can enhance the forward emission of incoherent ﬂuorescent sources embed- ded in a waveguide that also encloses the spiral. The enhancement occurs over a broad spectral band, proving the potential of Vogel’s golden spirals for broadband light-emitting devices
|||L. Langguth, A. Szuba, S. A. Mann, E. C. Garnett, G. H. Koenderink, and A. F. Koenderink, Nano-Antenna Enhanced Two-Focus Fluorescence Correlation Spectroscopy, Sci. Rep. 7, 5985:1–9, (2017).||(p)reprint DOI|