A secure identity optical device for anti-counterfeiting measures which is configured to produce visually (801, 902, 1004, 1103), spectroscopically (701), or microscopically (102, 103, 801, 902) verifiable security features wherein the optical device comprises at least:
- a substrate (201);
- and
- a plurality of optical scatterers (101, 202) being plasmonic nanoparticles affixed onto the substrate (201) and separated from adjacent scatterers (202) by a distance to form a two-dimensional pattern of said optical scatterers;
- characterized in that said optical scatterer pattern comprises at least one of:
- a) a specifically designed binary pattern (102, 105, 104, 801, 1003, 1101), wherein some scatterers either are (202) or are not (204) in a selected location on the substrate;
- b) a specifically designed colour-based pattern (103, 902), wherein some scatterers (902) scatter a measurably different colour of light compared to adjacent scatterers (901);
- c) a specifically designed photonic interaction between said scatterers (202), wherein said interaction results in features in an optical spectrum (701);
- or
- d) a combination of any of a), b) and c).