2. Key Laboratory of Information Storage System Ministry of Education of China, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China;
3. Shenzhen Huazhong University of Science and Technology Research Institute, Shenzhen, Guangdong 518057, China
Overview: Compared with the hard drive disk and solid state disk, longer storage lifetime and lower energy consumption data storage is required for Big Data centers. Optical data storage has the advantage of these two characteristics, but for traditional optical discs, such as blue-ray discs, their storage capacity is limited because of optical diffraction. Ultra high density optical storage has been extensively studied in recent years for its potential application for Big Data centers. Dual-beam super-resolution optical data storage has the potential to achieve petabyte capacity for a single standard disc by overcoming the optical diffraction limit. This dual-beam super-resolution storage technology combines technologies of dual-beam super-resolution laser nanofabrication and stimulated emission depletion (STED) microscopy. Dual-beam super-resolution laser nanofabrication can realize 9 nm feature size and about 50 nm feature resolution. STED microscopy has obtained a best resolution 5.8 nm at the current state of the art. Dual beam super-resolution optical data storage employees two lasers. One has a Gaussian shape of its focus plane, and the other is focused as a doughnut shape with zero intensity at the center. The doughnut shaped beam depletes the effect of Gaussian shaped laser interacting with materials in the processes of data recording and readout to acquire a resolution beyond the optical diffraction limit. For industrialization of dual-beam super-resolution optical data storage, we illuminate the key problems of storage medium, super-resolution data recording, super-resolution data readout and super-resolution positioning. The storage medium should be a solid film after disc fabrication, and have material property change such as fluorescence intensity enhancement induced by local illumination of the Gaussian shape laser to enable data recording and readout. The storage medium should be specifically designed to be capable of adopting the dual-beam approach to realize super-resolution. Except super-resolution recording and readout, super-resolution positioning technology is also required to guarantee position accurate data manipulation at the nanoscale. We propose a STED microscopy approach for super-resolution positioning in the super-resolution optical data storage setup. To simplify the optical system integration with a best achievable stability, separated super-resolution optical data recording and readout setup is suggested. The method to speed up data recording and readout is also discussed.