We present experimental results demonstrating the red-shifted photochromic behavior of a gelatin film made from L93T, a genetic variant of bacteriorhodopsin. The red shift of the absorbance spectrum on illumination with visible light is due to a short M-state lifetime and a longer-lived O state whose absorption peaks at 610 nm. Pump–probe measurements show the O state to have a lifetime of approximately 2.2 s in the gelatin film, with a single exponential decay behavior. We also present holographic kinetic results for both red (633-nm) and blue (442-nm) readout wavelengths.
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