Polarisation-independent enhanced scattering by tailoring asymmetric plasmonic systems.

Polarised light provides an efficient way for dynamic control over local optical properties of nanoscale plasmonic structures. Yet many applications that utilise control over the plasmonic near-field would benefit if the plasmonic device maintained the same magnitude of optical response for all polarisations. Here we show that completely asymmetric nanostructures can be designed to exhibit a broadband polarisation-independent and enhanced optical response. We provide both analytical and experimental results on two sets of plasmonic trimer nanostructures consisting of unequal nanodisks/apertures with different gap spacing. We show that, at certain inter-particle separations, enhanced far-field cross sections are independent to the incident polarisation, while still demonstrating nontrivial near-field control.