Bacteriorhodopsin, a light-transducing protein in the purple membrane of Halobacterium halobium, has unique properties that make it a potentially attractive material for use in optical imaging and processing. A transient diffraction grating based on the K intermediate of the bacteriorhodopsin photocycle has been produced on the nanosecond time scale. The diffraction efficiency, which would be sufficient for pattern recognition for example, was measured and the intensity dependence assessed.