Research On Typical Programmable Diffractive Optical Elements Based On Liquid Crystal On Silicon

With the development of science and technology,the modern optics and microelectronics are closely interpenetrated with each other and rapidly develop in the fields of optical communications,information storage.Therefore,the requirements that are the real-time processing of photoelectric information are also getting higher and higher.Although the traditional optical elements have the advantages of simple structure and excellent optical performance,they have a single structure of high cost and cannot flexibly meet the growing demand for the modulation of complex optical wavefront.Spatial light modulator is a device that plays an important role in optical signal processing.It can modulate amplitude,phase and polarization of light wavefront in real time.As a programmable optical wavefront modulation device of discrete structure,the LCOS is fabricated by using a CMOS silicon substrate and an aluminum layer,assemble liquid crystal displayed technology with silicon chip technology to control and drive the loading voltage of each pixel through standard graphic signal with computer interface,so that the two technologies of highly integrated and programmable modulation can work together.Due to its high diffraction efficiency,precise positioning,low power consumption,flexible modulation and other characteristics,and the traditional optical elements is gradually replaced by it,and has played an important role in optical information process.It has been widely used in interconnection of optical communications,laser guidance,glimmer and so on.The pure phase modulation LCOS is used as the carrier,the computational optics and diffractive optical elements are effectively combined to study a method of realizing diffractive optical element which has a positive effect on the development of photoelectric information processing.By designing the special functional software,calculating dynamically the phase pattern of the diffractive optical element is realized,and builds a bridge between the diffractive optical element and LCOS devices.The main research contents and innovations of the dissertation as follows:(1)An optical experiment simulation software is designed based on Lab VIEW,the mixed programming based on Lab VIEW and MATLAB is presented by taking advantage of high-level technical computing language of MATLAB and the characteristics of LabVIEW graphical language.The software interface is written in Lab VIEW,while its the optical simulation is written in MATLAB.The software realizes basic optics(lens imaging,light reflection),light diffraction(single slit diffraction,circular aperture diffraction,grating diffraction)and light interference(Film interference and multi-slit interference).At the same time,it integrates the simulations of the experiments which are holograms,the phase patterns of diffractive optical elements and so on.(2)Referring to low designed freedom and high cost of conventional optical element,a method of realizing programmable diffractive optical elements which are based on liquid crystal spatial light modulator is studied.Firstly,liquid crystal spatial light modulator with pixels structured characteristics analyzed;secondly,the phase modulation patterns of diffractive optical elements are encoded by computer;finally,the phase patterns of several typical diffractive optical elements(such as Fresnel phase lens,digital blazed grating,Axilens)are displayed on liquid crystal on silicon,thus the corresponding diffraction patterns can be obtained.The experiment results to verify the efficiency and accuracy of the method of the paper.Compared with conventional optical element,the proposed method can greatly improve the flexibility for fabricating the corresponding diffractive optical elements which are encoded by computer,which is suitable for various occasions for wavefront modulation.