Photochromic optical memory based on non-destructive IR read-out

The photochromic material 1-(2,5-dimethylthien-1,1-dioxide-3-yl)-2-(2,5-dimethylthien-3-yl)hexafluorocyclopentene (DMTFO2) undergoes reversible photocyclization and ring opening reactions upon alternate irradiation with UV and visible light, respectively. Upon photocyclization, the closed-ring isomer of DMTFO2 showed a strong IR absorption band at 1532 cm⁻¹ which was not observed for the open-ring isomer. To understand the IR spectra of DMTFO2, theoretical calculations were carried out using Gaussian 03 program at the B3LYP/6-31G(d) level. We also demonstrated non-destructive readout of photochromic recording by IR spectral difference between the open- and closed-ring isomers of DMTFO2 in film. We found that DMTFO2 exhibited a higher contrast ratio of IR image between open- and closed-ring isomer compared with previously reported 1,2-bis(2,5-dimethylthien-3-yl)perfluorocyclopentene (DMTF6) because of the increased photoconversion yield as well as higher vibrational transition intensity. These findings along with its high fatigue resistance indicate that DMTFO2 could be an excellent candidate for photon-mode RW (re-writable) memory devices based on photochromic recording and non-destructive IR read-out.