Study Of Supercritical Tightly Focused Multidimensional Optical Storage

The rapid expanding of global data storage market has constantly challenged the information storage techniques with higher capacities and lower energy consumptions.Although optical data storage has been well heralded as a green solution,the diffraction limit makes it difficult to further improve its storage capacity.To tackle this challenge,tremendous progresses have been achieved recently by optical multiplexing through creating orthogonal data channels in the physical dimensions of light or breading the diffraction limit through superresolution recording techniques.This work introduces the research of super-resolution multi-dimensional optical storage by combining multi-dimension multiplexing technology and super-resolution technology.The first part of this thesis mainly focuses on the design of supercritical focusing phase and the characterization of supercritical focusing spot.The population number,crossover probability,mutation probability and objective function in genetic algorithm are set,and the supercritical phase is obtained through population iteration.The supercritical phase is numerically verified by vector Debye diffraction integral to achieve a focus of 0.38λ/NA,whereλIs the wavelength of the incident light,and NA is the numerical aperture of the objective lens.The point spread function of the supercritical focal point was successfully characterized by raster scanning of a gold particle and the upconversion fluorescence particle Na YF₄:Nd³⁺/Yb³⁺/Er³⁺.It was successfully verified that the supercritical tight focusing has higher imaging resolution than the unmodulated focusing.The second part of this thesis mainly focuses on the preparation of multilayer optical disks and multi-dimensional optical storage under supercritical focusing.Because the hot spots formed by randomly coupled gold nanorods have polarization wavelength dependence,gold nanorods are selected as the recording medium of multidimensional optical disks.By mixing gold nanorods with polyvinyl alcohol at a ratio of 1:3,a recording layer with a thickness of 1μm was prepared,and an isolation layer with a thickness of 10μm was prepared with transparent HC003.Finally,single layer,three-layer,five-layer and even ten-layer optical discs are realized by repeating preparation of recording and isolation layers.The absorption spectrum of gold nanorod solution,the transmission spectrum of optical discs and the layer by layer fluorescence uniformity of optical discs were characterized.The size of 400 nm recording point is realized in optical discs by supercritical focusing,and the density of storage surface is increased 36%.In addition,the physical dimension of polarization and wavelength multiplexing are demonstrated successfully,and the five-layer storage with dual wavelength and dual polarization is recorded in five-layer optical disks.At last,phase modulation is utilized to compenstate the refractive-index mismatch induced aberration to achieve high-fidelity and low power recording.