| Holographic data storage (HDS) systems are advantageous high-density data storage systems due to their high data transfer rate. Lack of suitable recording materials for read-without-erasure using light of the same wavelength as the recording light has been the primary obstacle of HDS systems. I present a novel method of using a unique biological material, bacteriorhodopsin (BR), to overcome this obstacle.;This new method utilizes two distinct states of BR, known as the blue membrane (BM) state and the purple membrane (PM) state. Illumination with red light on the BM state induces a photo-intermediate state, the Q state, which is transparent to red light and has an indefinite lifetime. The Q state is not induced from the PM state by visible light. A hologram is recorded on a BR film initially existing in the BM state using red light. After recording, the BR film is "switched" so that the BR material in the BM state is converted to the PM state while the Q state is left unchanged. Since both the PM state and the Q state are insensitive to red light, light of the same wavelength as the recording light is used to read out data without erasing the hologram. Switching BR between the PM state and the BM state is controlled by a low electric field (2 V/cm).;Site-directed mutagenesis was used to improve the optical properties of the BM state by manipulating BR molecule. Improvement of the optical properties was found in BR mutants, D85N, Y185F, and D85E. Information obtained from this study provides guidelines to optimize BR for HDS systems. |
