Composite Optical Materials for Mechanical Deformation

A composite optical device has a layer of a composite optical material mounted on a substrate. The layer of composite optical material has substantially uniform thickness. The composite optical material is a polymer opal, in that it has a three dimensional arrangement of core particles distributed in a matrix, the refractive index of the material of the core particles being different to the refractive index of the material of the matrix and the three dimensional arrangement being capable of having a periodicity such that, when a surface of the material is illuminated with white light, the composite material exhibits structural colour. The local stiffness of the substrate is different at different positions of the substrate. The effect of this is that, on mechanical deformation of the composite optical device, the substrate is deformed to a different extent at different positions of the substrate and the layer of composite optical material is correspondingly deformed to a different extent at different positions of the layer of composite optical material. This provides local variation in the structural colour response of the layer of composite optical material on mechanical deformation of the composite optical device.