A method for encoding information that is encoded in spatial variations of the intensity of light (24) of a first wavelength into light of a second wavelength, the method comprising: generating a first density distribution of electrons homologous with the spatial variations in intensity of the first wavelength light; generating a second additional electron density homologous with the first electron density distribution; trapping electrons from the first and second electron density distributions in a trapping region (34) to generate an electric field homologous with the density distributions in a material (36) that modulates a characteristic of light (22) that passes therethrough responsive to an electric field (46) therein; and transmitting the second wavelength light (22) through the modulating material (36) thereby modulating the second wavelength light in response to the electric field and encoding it with the information.