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A dithienylethene derivative having bulky substituents, 1,2-bis(5-(2,4-diphenylphenyl)-2,4-dimethyl-3-thienyl)perfluorocyclopentene (1a) was synthesized in an attempt to prepare photochromic amorphous films. 1a formed a stable bulk amorphous state at room temperature and the glass transition temperature was observed at 82°C. The conversion ratio from 1a to the closed-ring isomer (1b) upon irradiation with 303 nm light was as high as 73% in the amorphous film. Rewritable photon-mode near-field optical recording was demonstrated with the amorphous thin film of 1b.

Novel nondestructive readout methods for near-field optical recording has been demonstrated with an amorphous photochromic film. Large refractive index change of an amorphous photochromic layer of 1,2-bis(5-(2,4-diphenylphenyl)-2,4-dimethyl-3-thienyl) perfluorocyclopentene induced by the photochromic reactions is detected by the use of a guided-wave mode and a substrate radiation mode with near-IR laser light. The modulation amplitude in the reflected light intensity before and after the photo-bleaching reaction was as high as 20%.