A data storage medium for storing digital data. The medium includes a mixture of different nano-sized materials, each of the nano-sized materials having a respective optical transition profile characterizing an optical transition of the nano-sized material and covering a respective wavelength range, wherein a combined optical transition profile of the mixture covers an extended wavelength range as compared to the respective wavelength ranges of the respective optical transition profiles of the different nano-sized materials, and wherein one or more of the different nano-sized materials is photo-reactive to selectively vary a respective absorption/emission band upon irradiation to encode digital data in the combined optical transition profile of the mixture.