Dual-use chromophores for photorefractive and irreversible photochromic applications

Holographic experiments are performed on a series of dual-use chromophore molecules wherein both irreversible photochromic and erasable photorefractive holographic gratings can be written in the same storage volume. At 675 nm, the chromophore undergoes a photochemical reaction leading to the creation of irreversible holographic gratings. Alternatively, at longer wavelengths, application of an electric field during grating formation allows the storage of erasable photorefractive holograms in the same location as previously stored permanent photochemical holograms. Photochemical gratings (η > 60%) can be written in less than 1 min, whereas photorefractive gratings (η > 50%) can be written in less than 1 s. The photochemical gratings have a diffusion-limited dark half-life of as long as two weeks depending on the glass transition temperature of the composite.