Book excerpt: Biochrome photosensitive films in particular Bacteriorhodopsin exhibit features which make these materials an attractive recording medium for optical data storage and processing. Bacteriorhodopsin films find numerous applications in a wide range of optical data processing applications; however the short-term memory characteristics of BR limits their applications for holographic data storage. The life-time of the BR can be extended using cryogenic temperatures [1], although this method makes the system overly complicated and unstable. Longer life-times can be provided in one modification of BR - the "blue" membrane BR [2], however currently available films are characterized by both low diffraction efficiency and difficulties in providing photoreversible recording. In addition, as a dynamic recording material, the BR requires different wavelengths for recording and reconstructing of optical data in order to prevent the information erasure during its readout. This fact also put constraints on a BR-based Optical Memory, due to information loss in holographic memory systems employing the two-lambda technique for reading-writing thick multiplexed holograms.Mehrl, David J. and Krile, Thomas F.Ames Research CenterCRYOGENIC TEMPERATURE; HOLOGRAPHY; DATA STORAGE; OPTICAL DATA PROCESSING; OPTICAL MEMORY (DATA STORAGE); BACTERIA; MULTIPLEXING; PHOTORECEPTORS; LOSSES; DIFFRACTION