Broadband light scattering and photoluminescence enhancement from plasmonic Vogel's golden spirals

Periodic arrays of plasmonic nanoantennas can enhance the directionality of light emission of nearby fluorophores and, therefore, have a great potential for a broad range of applications. 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 for periodic structures: 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. Combining k-space Stokes polarimetry and theoretical calculations, we first investigate the light scattering from Vogel's arrays and the coupling between individual nanoantennas. Next, photoluminescence measurements show that the spirals can enhance the forward emission of incoherent fluorescent sources embedded 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.