Polarization-encrypted high-resolution full-color images exploiting hydrogenated amorphous silicon nanogratings

Abstract As a prominent alternative to toxic dyes/pigments, nanostructural color pixels have garnered tremendous attention in applications related to display/imaging devices and color printings. However, current color pixels mostly offer static color responses. In relation to this, dynamic color tuning properties must be investigated in order to expand their functionalities and promote their use in the fields of encryption and anti-counterfeiting. In this study, a simple array of hydrogenated amorphous silicon nanogratings is proposed to realize polarization-encrypted full-color images via the coupling of incident light into different leaky mode resonances within the nanogratings. The proposed pixels can readily switch from vivid full colors to indistinguishable orange color by altering the incident polarization state. Hence, unlike the reported polarization-tuned color generation schemes that merely allow for the color variation of the image or require complicated designs to hide the color information, the proposed approach can encrypt arbitrary full-color images via a simple tuning of the incident polarization state. Owing to the localized leaky mode resonances supported by the nanogratings, the pixel can still implement the polarization-encrypted functionality even when it contains only four gratings, thus enabling a remarkably high resolution. The proposed simple scheme may provide a credible new pathway for accelerating the practical applications of high-resolution encryption and anti-counterfeiting.