A novel diarylethene, namely 4,5-(2,5-dimethyl thiophene) phthalimide, was synthesized and successfully introduced to rewritable holographic data storage. Upon the alternative illumination of UV and visible light (>400 nm), this compound underwent rapid, reversible inter-conversion between colorless open-ring isomer and yellow-green ring-closed form in both solution and polymethyl methacrylate (PMMA) film. Subsequently, we investigated the characteristics of volume homographic recording of the diarylethene-doped PMMA film (1 m thick). The maximum refractive index modulation (0.87‰) of the film during recording could be reached within just 120 s which gave the ability of fast recording. The high quality reconstruction after 50 write/erase cycles demonstrated its excellent fatigue-resistance and high resolution. All those results indicated that this molecule was a reliable fast write/erase holographic storage material. With the development of information science, the demands for large storage systems are increasing daily. Optical data storage was always a very important storage technology for the advantage that the reading and writing of the digital data did not require contact and was therefore wear-free [1]. The optical data-storage formats, currently on the market such as compact disc (CD), digital versatile disc (DVD), Blue-ray disc (BD) and high density DVD (HD DVD), were based on the principles of far-field optics. For those formats, the storage density therefore followed the far-field optics scaling law NA/ 2 , where NA stands for numerical aperture and is the wavelength of the recording light. Theoretically, the storage density could be increased by reducing and increasing the NA. However, with the advent of BD, the planar data storage has already reached its upper limit [2,3]. Holographic data storage used the entire volume of the storage medium. The data could be arranged in multiple information layers, which made it provide large storage capacity easily. The density potential reaches V/ 3 , where V denotes the recording volume and is the wavelength of the recording light source. In addition, holographic memory was a defect-tolerant device since each bit of information was generated from the entirety of a holographic memory. In view of these factors, holographic volume memory was long envisioned as the next generation storage technology [4]. Photochromism was defined as a transformation of a single chemical species between two states that have different geometrical structures, absorption spectra and refractive index, etc. The change was achieved by the illumination of lights with different wavelengths. When using photochromic materials in holographic storage, the refractive index of the photochromic molecules in the film would get changed with the laser irradiation. The holographic diffrac-
