Laser Modification Of Luminescent Materials And Multi-dimensional Optical Storage Research

The explosive growth of the global data volume demands new and advanced data storage methods.Compared with the traditional storage method of laser modified refractive index,fluorescence-based optical storage has more storage dimensions such as intensity,wavelength,phase and polarization.In this paper,the fluorescence modification of perovskite thin films CH₃NH3Pb I₃（MAPb I₃）,transition metal sulphide WS₂ and its alloys,and transparent plastics can be realized by laser regulation,respectively.According to their luminescence regulation mechanism with laser irradiation,operational feasibility and so on,their feasibility as an optical storage medium is explored.The main contents of this paper are as follows:（1）The relationship between luminescence properties of organometallic halide perovskites（OHPs）and laser irradiation has been studied.Here,we demonstrate that luminescence of CH₃NH₃Pb I₃（MAPb I₃）is governed by light irradiation induced oxygen curing and vacancy-mediated ion migration.The luminescence increases under continuous irradiation because of the curing of iodine vacancy（V_I）by oxygen.Whilst,it decreases with enhanced ion migration,which would induce excess trap states.The existence of V_I is proved by low temperature photoluminescence（PL）spectra,hysteresis effect in J-V curves and excitation density dependence of PL lifetime.Different oxygen environments and applied bias are employed to control the degree of oxygen curving and ion migration.These results provide a perception on the correlation of the complicated influencing factors affecting the luminescence of OHPs for accelerating the process of its application.（2）The relationship between luminescence properties of transition metal dichalcogenide chalcogenides and laser irradiation has been studied.It is found that ozone pretreated materials are very sensitive to laser so the storage capacity within<1 nm thickness could be up to～62.5MB/cm² with fast writing speed.Moreover,we demonstrate the thinnest light disk at atomic level via developing an erasable method to directly write encrypted information onto WS₂monolayers.Density functional theory（DFT）calculations suggest that the disk formatting is realized by ozone molecule adsorption induced localized unoccupied states,while the read-in relies on the passivation of defects via substitution of the sulfur vacancies with oxygen atoms.（3）The relationship between luminescence properties of transparent plastic and laser irradiation has been studied.It is found that fluorophore will be generated in the area irradiated by femtosecond laser,so as to realize multi-dimensional information storage.Via direct fs laser writing,the broad variation of fluorescence intensity assigns 8 gray levels,corresponding to 3bits on each spot,in transplant plastics.Here,we report that the polycarbonate（PC）,precipitated calcium carbonate（PCC）,polystyrene（PS）,and polymethyl methacrylate（PMMA）is all suitable.The focused fs laser can modify the fluorescence of written regions on the surface and in the interior of PMMA,enabling three-dimensional（3D）information storage.Through the3D laser processing platform,a 50-layer data record with low bit error（0.96%）is archived.Visual reading of data empowered by the fluorescence contrast proved data storage with ultrahigh capacity（～1 TB per disc）can be realized in transplant plastics.In summary,we studied the influence of laser modification on the luminescent properties of materials,and tried to apply it to multi-dimensional optical storage.We believe that this research will contribute to the development of high-density and high-capacity optical storage based on the interaction between light and matter.