NANOSECOND OPTICAL-EXCITATION DYNAMICS OF LONG M-STATE LIFETIME BACTERIORHODOPSIN FILMS

Dynamic parameters relevant to the performance of bacteriorhodopsin (b R) as an optical cache memory are reported. The thermal relaxation of the M-state photocycle-intermediate has been a barrier to the exploita tion of wild-type bR in optical memory devices. Extension of the room- temperature M-state lifetime from 10 ms to similar to 10 s is describe d. Writing to the long-lifetime material is achieved for nanosecond pu lses of less than 1 nJ mu m(-2) fluence. Reading, at a contrast-ratio of 1.3:1, is achievable following a 5 ms delay. Erasure is achieved on a 50 mu s timescale for pulse fluences similar to those used for the writing stage. Following continuous-wave (cw) excitation, contrast rat ios of 200:1 are obtained, with significant photochromic changes remai ning after many seconds.