Optical storage in pentaalkinylbenzene derivatives. Strong gain effect by recrystallization processes

Optical storage experiments were performed on pentaalkinylbenzene derivatives carrying functional azobenzene groups as well as on equimolar mixtures with the acceptor TNF. These materials are partially crystalline yet can be prepared in an amorphous state. The light-induced optical responses, i.e., the diffraction efficiency of an induced grating, was rather weak for amorphous films as prepared by spin-coating. Strong amplification effects occurred, however, on a subsequent annealing step performed with the writing light switched off. The diffraction efficiency was found to increase by more than a factor of 500. This strong gain effect is controlled by the selective growth of crystals in the nonirradiated areas.