Research On Vortex Converging Lightwave And Surface Plasmon Generation Method For High Density Optical Storage

Currently,there are two main information storage methods including magnetic storage and optical storage.Optical storage with several characters including low power consumption and high stability,still demonstrates a relatively low storage density because of current light diffraction limit.As shown in previous studies,the light diffraction limit can be breaked effectively through utilizing surface plasmons(SPs)effect to highly localize incident lightfield into very small a space in the nanometer scale.The excitation of SPs must simultaneously satisfy the energy and momentum conservation relationship.For developing photo-magnetism optical storage technology,the momentum characteristic of magnetic effect has become a key research factor.As a kind of lightwave mode fully displaying a special momentum character,the vortex lightfields will play an important role in researching SPs excitation for performing photo-magnetism ultra-high density optical storage.In this paper,a convex arc-shaped spiral phase structure for generating a kind of vortex convergent beams and an arrayed double-nested-diamond metal micro-nano-structure(DNDMM)for exciting SPs,are designed.In addition,the careful simulation and structural fabrication and optical testing evaluation of the above micro-nano-optical structures are carried out for verifying the effectiveness of the structural designs.The basic work mentioned above lay a key device foundation for exciting SPs by vortex beams focused over the surface of the DNDMM array for breakthrough light diffraction limit and therefore realizing photo-magnetism ultra-high density optical storage.The main work is as follows:First,a DNDMM array is designed for exciting SPs lightfield to break light diffraction limit.Based on typical spiral phase structure,a convex spiral phaser array is designed for generating vortex convergent beams.By changing parameters including metal film material,film thickness,and micro-nano-structure coefficients of the DNDMM,the SPs excitation characteristics under different parameter configuration are simulated and analyzed.Furthermore,through optimizing the micro-nano-structure parameters,a strong light absorption of ?87.79% is obtained at the wavelength of 630.7nm.The typical properties of the vortex beams for exciting SPs are simulated and analyzed.Under the current condition with a relatively low simulation accuracy,the SPs lightfield effectively excited by vortex converging beams can be observed clearly.Then,a DNDMM array for exciting SPs is fabricated using a focused ion beam etching.Observation by electron microscope reveals that the inner diamond-shaped tips are already blunted due to the machining accuracy,but the obtained micro-nano-structure is still intact and the outline edge clear.An arrayed spiral phaser is successfully fabricated by 3D printing method of the modern additive manufacturing technology.The surface morphology testment demonstrates that the structure morphology is clear and complete,and the surface processing accuracy ?200nm,which already met the design requirements.A scattering near-field optical microscope is used to perform optical test and evaluation of the DNDMM array.The testament results show that under the illumination of the beams of 633 nm wavelength,a "linear-circular dual lightspot set is generated over both the edges and the central nano-column of the arrayed DNDMM.The average length of the linear lightspot is in a range of 0.6?m?1?m,and then its average width in a range of 45nm?50nm,which already breaks the light diffraction limit.The diameter of the quasi-circular lightspot is in a range of 33nm?50nm so as to far exceed the light diffraction limit,which already decreases an order of magnitude compared with excitation light wavelength,and constructs a strong localized lightfield.To the fabricated spiral phaser array,four different light wavelength are used for testing and evaluation its optical characteristics.It should be noted that the vortex beams firstly present a clockwise rotation and then incident upon the focal plane with a circular lightfield appearance and thus convert into counterclockwise vortex,which means an obvious vortex shifting,so as to lay an optical foundation for exciting SPs by vortex beams.