A method of manufacturing a plasmonic device having a base substrate and an electrically conductive film formed on the base substrate, wherein the base substrate has a reference upper surface and an arrangement of chiral nanostructures formed in relief from the reference upper surface, each chiral nanostructure having a nanostructure upper surface which is disposed at a distance of at least 30 nm from the reference upper surface in a thickness direction, wherein the electrically conductive film is formed on the nanostructure upper surface of each chiral nanostructure and on at least part of the reference upper surface of the base substrate, the method including the steps:
- providing the arrangement of chiral nanostructures by moulding of the base substrate;
- and then
- forming the electrically conductive film on the nanostructure upper surfaces and the reference upper surface.