On October 29th, Prof. Jingyu Zhang, from Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, led a team to publish the recent research advances in OPTICS LETTERS, “Anisotropic nanostructure by spatial-temporal picocond pulse for multidimensional optical data storage”.
According to estimates by the International Data Center, by 2025, the world will generate up to 175ZB of total data that year, and the explosive growth of data in the current era highlights a number of problems with data storage technologies, including high energy consumption, low capacity, and short lifetime. Optical data storage has the advantages of large capacity, long lifetime and environmental-friendly. It is ideal for storing large amounts of digital data. However, to further increase its lifetime and capacity is a forbidden task for traditional diffraction-limited polymer-based optical disc systems. As a result, new technologies such as holographic, multi-dimensional and super-resolution data storage have been developed.
However, from the perspective of practical applications, many of the most advanced technologies require multiple laser pulses or long-term laser exposure to form a single data voxel structure, which greatly hinders the data writing speed. In nanoplasmonic hybrid glass, the data writing of each multiplexed data voxel requires several tens of milliseconds of laser irradiation. Furthermore, a four-step millisecond-scale writing procedure was required to record a diffraction-unlimited data spot based on photoswitchable fluorescent proteins. Five-dimensional optical data based on nanograting structure has successfully stored digital data in glass with an unlimited lifetime. However, due to an incubation effect, this structure requires multiple laser pulses to generate. In order to reduce the overall laser irradiation time, many studies have been conducted.
In this paper, the researchers report that anisotropic nanostructures generated in fused silica by manipulating the spatial and temporal distribution of a picosecond beam and are used for high-speed writing of multidimensional optical data storage in glass. The delay line and the spatial light modulator (SLM) are used to implement the spatiotemporal manipulationof the picosecond pulse. A parameter sweep experiment was conducted. The parameters include delay time, relative position, pulse energy, pulse energy ratio and polarization states of two pulses.The anisotropic structure can be produced in fused silica glass by the spatiotemporal manipulated picosecond pulse. The generation of this birefringent structure is attributed to the time-domain characteristics of inter-band excitons generated and the refractive index increase after femtosecond laser irradiation. This method can simplify the pulse processing process and achieve high-speed MB/s data writing. In addition, by controlling the spatial-temporal characteristics of pulses, oblique nanostructures with any three-dimensional orientation can be generated. Thus, six-dimensional optical data storage technology could be implemented in the near future.
This work is supported by Creative Research Group Project of NSFC (Grant Nos. 61821003), Creative Research Group Project of NSFC, and Program for HUST Academic Frontier Youth Team. This paper is jointly collaborated with Mr Zhi Yan, Mr Peiyao Li, Mr. Jichao Gao, Dr. Jingyu Zhang from Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Dr. Yuan Wang from Department of Physics, Huazhong University of Science and Technology, Dr. Wang Lei from Jilin University, and Dr. Martynas Beresna from University of Southampton.
FIG.1 (a) Schematic illustration of the setup. (b) Schematic illustration of the setup with a birefringent crystal (BC). (c,d) Schematic diagram of femtosecond pulse spatial distribution
FIG.2 Top-view birefringent (a) and SEM images (b) of anisotropic nanostructure. (c) Slow-axis orientation image of the recorded multi-diemensional voxel array
