Polarisation conversion and optical meron topologies in anisotropic epsilon-near-zero metamaterials

Plasmonic metamaterials provide a flexible platform for light manipulation and polarisation management, thanks to their engineered optical properties with exotic dispersion regimes. Here, we exploit the enhanced spin-orbit coupling induced by the strong anisotropy of plasmonic nanorod metamaterials to control the polarisation of vector vortex beams and generate complex field structures with meron topology. Modifying the degree of ellipticity of the input polarisation, we show how the observed meron topology can be additionally manipulated. Flexible control of the state of polarisation of vortex beams is important in optical manipulation, communications, metrology and quantum technologies.