Abstract: A security device, including at least first and second embossed, reflective metal diffraction gratings in respective regions: wherein the first diffraction grating exhibits, in incident white light, a zero-order output over a first area of substantially uniform grating period, wherein the zero-order output of the first diffraction grating comprises different coloured first and second sub-outputs for respective first and second polarisations parallel and perpendicular to the first diffraction grating; wherein the second diffraction grating exhibits, in incident white light, a zero-order output over a second area of substantially uniform grating period; wherein the zero-order output of the second diffraction grating comprises third and fourth sub-outputs for respective first and second polarisations parallel and perpendicular to the second diffraction grating; and wherein the first and second diffraction gratings exhibit, for incident white light, substantially the same first order diffraction efficiency over t

Abstract: A method of creating a security product includes providing a substrate, depositing a discontinuous layer of electrically conducting material on the substrate, and laser-annealing the discontinuous layer of electrically conducting material to generate nanoparticles exhibiting a surface plasmon resonance effect.