Optical information storage of bacteriorhodopsin molecule film

The photochromic retinal protein bacteriorhodopsin (BR) is found in the cell membrane of Halobacterium salinarium. It is the key protein for photosynthetic growth of H. salinarium. BR shows an exceptional stability towards chemical, thermal, and photochemical degradation. In this paper, we propose a system of optical information storage in a BR polymer film. A three-wavelength EDRAW (Erase Direct Read After Write) experiment was performed. The photoexcited P(490) state shows a permanent storage property confirmed by our contrast ratio experiments. We have performed the reversible operations of `write' and `erase' with the BR polymer film over hundreds of cycles in our experiments. The readout contrast ratio is very sensitive to the intensity and wavelength of probe beam and the recorded data can be readout from 530 to approximately 630 nm with different contrast ratio. Within the range of 570 to approximately 600 nmm, the better contrast ratio can be obtained. Considering the erasing effect for the reason of absorption of P state, both higher contrast ratio and nondestructive reading can be realized by using 594 nm as the readout wavelength. The experimental result such BR material is very suitable for long-term photochromic information storage.