The diarylethene may undergo photochemical ring-closing reaction and both photochemical and electrochemical ring-opening reaction. Irradiation of the open form with UV light results in essentially quantitative photocyclization to the deeply colored form. The dithienylcyclopentene derivative in their ring-closed forms can undergo ring-opening upon electrochemical oxidation.
Although recordable disk are rapidly developing, the mainstream in the market is still the read-only manufactures such as CD-ROM and DVD-ROM which have prerecorded information. How to enhance the storage density of read only memory is one of the hotspots in optical data storage. The authors put forward novel theory for read only memory. The novel theory takes little organic molecule as memory medium of read only memory, and the writing process is photon-mode, which is called organic photonic read only memory (OP-ROM). According to the novel theory, disks can be massively copied by exposure. Furthermore, because of diversity and modifiability of organic molecules, the storage density can be improved by multi-wavelength, multi-level and multi-layer.
3D optical data storage can benefit from the non-linear process of two-photon absorption (TPA). If some chromphores with large TPA cross section are introduced into the diarylethene to enhance its two-photon absorptivities, it is expected to be good recording media for 3D optical data storage. The authors have synthesized four diarylperfluorocyclopentene (DPFCP) derivates for the purpose of developing two-photon 3D optical data storage. The nonlinear two-photon absorption (TPA) properties of the compounds were examined, and the reaction and excited state relaxation dynamics after two-photon excitation were investigated. The TPA cross sections of 2-position DPFCPs were measured by means of TPIF (two-photon induced fluorescence) method, and the highest is 48×10<sup>-50</sup>cm<sup>4</sup>•s•photo<sup>-1</sup>•molecule<sup>-1</sup>. The compounds were successfully applied in two-photon 3D optical data storage based on single beam two-photon femtosecond writing and one-photon fluorescence reading. Ten-layer clear images on DPFCP/PMMA film were obtained, and the data storage density is high to 2.0×10<sup>11</sup> bits/cm<sup>3</sup>.