Large forward scattering of light with balls of silver nanoparticles

What is it about?

The Huygens-Fresnel principle is an important physical theorem that states that every point of a propagating plane wave is equivalent to the continuum of point sources of hermispherical wavelets that propagate in the direction of propagation of the wave. Such soures are referred to as Huygens sources and have remained a mathematical commodity used by physicists to explain wave phenomena such as diffraction and refraction. Nonetheless making them real is useful, in particular if the phase of the wave can be controlled, because they hold the potential to shape light with a single layer of such sources. In this work, plasmonic balls made of ensembles of silver nanoparticles are designed and fabricated and shown to exhibit strong, broadband forward-scattering across the visible range, thus acting as Huygens sources and showcasing their potential use as meta-atoms for bottom-up metasurface applications. A physical understanding of the complex interferences occurring in such a system is provided.

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Photo by Constantin on Unsplash

Photo by Constantin on Unsplash

Why is it important?

Particulate media such as these balls that come in the form of clusters are notoriously difficult to simulate, let alone fabricate to achieve a controlled optical property. Here, not only is a dense particulate media composed of more that a hundred resonating particles designed numerically, but it is also fabricated to achieve an important optical property: that of strong forward light scattering at a subwavelength scale, a property of prime importance to the domain of metamaterials and metasurfaces.

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