Research On Ar Diffraction Waveguide Based On Femtosecond Lsaer Micro-nano Lithography

Augmented reality display technology superimposes the display of real scenes and virtual information,allowing users to see both the real scene and the virtual scene generated by the computer.Due to the unique of display,AR has a wide range of application values in military,medical and health,education,navigation system and other fields.At present,Optical waveguide technology is an important direction of AR research.According to the difference of diffractive elements,optical waveguide technology can be divided into holographic optical waveguide and surface relief grating optical waveguide.Compared with holographic optical waveguides,the surface relief grating optical waveguide has the characteristics of large field of view and high diffraction efficiency.At the same time,with the advancement of micro-nano manfacturing technology,surface relief grating optical waveguides have become the best choice for making AR waveguide glasses.The research of relief grating waveguide based on femtosecond laser micro-nano lithography is presented in this paper.The femtosecond micro-nano lithography system mainly utilizes the principle of bimolecular polymerization of photoresist and the nonlinear absorption effect to break through the diffraction to achieve nano process.Traditional electron beam lithography is expensive,It is not suitable for experimental research.In this paper,a 780 nm femtosecond laser direct writing micro-nano machining platform is established.The process of systematic machining of microstructure was studied and the structure of the relief grating waveguide is simulated theoretically.The structure of the relief grating is processed and made.Finally,the grating structure is tested and analyzed.The main work of this paper can be divided into the following parts:1.Firstly,the article studies the development history of augmented reality,it introduces the composition of diffraction optical waveguide display system and according to the different diffractive element is divided into holographic optical waveguide and the surface relief grating optical waveguide,form the field of view,the diffraction efficiency of the waveguide holographic grating and to compare the difference of surface relief grating,embodies the surface relief grating has obvious advantage in makingdiffraction optical waveguide.2.The processing technology of the femtosecond laser micro-nano lithpgraphy system was studied.The exposure principle of photoresist and the principle of bimolecular polymerization effect are introduced,and the factors that affact the efficiency of bimolecular polymerization are studied.Then the study of the system processing resolution,through the experimental method,laser power,scanning speed,analog structure design and other important parameters on the micro-nano structure resolution of the prepared,tested the best parameter performance of the system,to ensure the stability and efficiency of the relief grating processing.3.The theoretical simulation model of relief grating optical waveguide is designed.Through the simulation,the corresponding relationship between the grating structure parameters and the waveguide system field of view is analyzed,and the grating structure is designed to optimize the field of view.The method of extending the relief grating waveguide system field of view is established.The finite element analysis method is used to calculate the periodic grating structure.4.The grating structure was fabricated and tested by the femtosecond micro-nano lithography system.The final machined slanted relief grating has a structure area of1mm×1mm and can achieve a field of 26°,consistent with simulation results.