A method for storing holographic data, said method comprising: step (A) providing an optically transparent substrate comprising a polymer composition and a light absorbing chromophore, said polymer composition comprising a continuous phase and a dispersed phase, said dispersed phase being less than about 200 nm in size; and step (B) irradiating a volume element of the optically transparent substrate with a holographic interference pattern, wherein the pattern has a first wavelength and an intensity both sufficient to cause a phase change in at least a portion of the dispersed phase within the volume element of the substrate to produce within the irradiated volume element refractive index variations corresponding to the holographic interference pattern, thereby producing an optically readable datum corresponding to the volume element.