Photochromic transformations in doped polymers upon two-photon excitation

Physical photochromic transformations are studied in doped polymer films upon two-photon excitation. It is shown by the example of fluorescein halogen derivatives that the triplet-level population of molecules can be controlled by exciting the system by light into the T₁ → T_n triplet – triplet absorption band of molecules. It is proposed to use this effect for fabrication of materials with controllable photochromic properties.