Volumetric optical memory based on bacteriorhodopsin

An architecture for a three-dimensional optical computer memory based on the photoactive protein bacteriorhodopsin (BR) is described, utilizing a branch-off of the BR photocycle to access a long-lived photointermediate capable of serving as an active element for memory storage. This intermediate (the Q-state) is accessed as a result of the sequential absorption of two photons, the first to initiate the BR photocycle, and the second to drive the protein into the branched photocycle from the O-state several milliseconds later. The stability of the Q-state arises predominantly from the fact that it is strongly blue-shifted with respect to other intermediates in the photocycle, making it invisible to the laser wavelengths used to write and read information in the memory. Both proof of principle and second-generation prototypes are currently being developed in the W.M. Keck Center for Molecular Electronics, in collaboration with Critical Link, LLC of Syracuse, NY. The article will focus on the BR-branched photocycle memory architecture, the remaining challenges to fabrication of a commercially viable device, and the ongoing efforts in prototype development, optimization and protein characterization at Syracuse University.