On The Model Of Phase Modulation Device Upon Deep Sub-wavelength Grating Structure

Display technology provides the carrier and means for the visual information,is one of the key technologies of the information society.Holographic technology has been recognized as the most promising 3D display technology,because it can produce a perfect realistic three-dimensional scene.The key device of the holographic display is the spatial light modulator(SLM),holographic video display devices need to achieve sufficient space bandwidth,which requires the size of the device unit close to the wavelength of light,of course sufficient diffraction efficiency and phase modulation are also required.The available commercial LCOS is one of the widely used spatial light modulator.However,the commercial LCOS achieves phase modulation through the optical path difference of the liquid crystal,which is not conducive to the further reduction of the device to achieve the spatial bandwidth required for the holographic display.Surface plasmonic technology provides an effective method for manipulating light at sub-wavelength scales,including the modulation method of optical phase,which provides a new method to solve the bottleneck problem of holographic video display.In this paper,the optical phase modulation characteristics of the metal grating coupled structure and the dielectric grating coupled structure are studied,and the phase modulation of light is manipulated at sub-wavelength scale.Because metal-dielectric-metal(MDM-like waveguide)structure can enhance the modulation effect of metal grating and similar to the commercial LCOS structure,it can provide some process consistency for the actual fabrication of future devices.In the design,Consider similar to LCOS structure.The specific design is that the top ITO electrode layer of current LCOS is replaced by metal sub-wavelength grating,while retaining the original liquid crystal layer and cell drive layer structure.Although the structure is similar,the physical effect of the liquid crystal layer of the new device is completely different.It is a novel phase modulation device model,which can realize manipulating light at sub-wavelength scale and reach the phase modulation range of[0,2?].The main research work and innovation of the paper are as follows:1)In this paper,the metal-dielectric-metal three-layer structure model and dielectric-dielectric-metal three-layer structure model are improved.Based on the principle of F-P resonance,studying the different mechanisms of grating resonance,it is verified that there is an abnormal resonant mechanism in sub-wavelength gratings.The optical properties of the two sub-wavelength grating coupling models are analyzed by FDTD and CST.The ability of manipulating the optical phase on the sub-wavelength scale is analyzed.The anomalous reflection mechanism of the F-P resonance in the grating coupled structure is verified by experiments.2)In this paper,the metal-medium-metal three-layer structure model and the medium-dielectric-metal three-layer structure model are studied in the visible light band,based on the coupling physics of Fabry-Perot(FP)resonance and metal surface plasmon in deep sub-wavelength metal grating,the horizontal and vertical resonance mechanisms in the grating slits are studied,and their capacity of manipulating light at sub-wavelength scale is analyzed,two kind of sub-wavelength grating coupling models are designed.The performance of the two sub-wavelength grating coupling structures is verified by FDTD Solution and CST simulation software.3)Usually,Au and Ag are used in plasma materials,and this paper verifies the feasibility of aluminum as a plasma material and its advantages.In the current literature about surface plasmas,aluminum is generally not considered to be an attractive plasma material,but it is resource-rich,inexpensive and compatible with CMOS,it is widely used in commercial spatial light modulators,such as LCOS.It is well known that aluminum plasma properties are sensitive to the geometry of the material.However,we have effectively overcome these problems in the design of sub-wavelength grating coupling structure.The simulation results also show that when the aluminum nanorods in aluminum gratings change from 140 nm to 190 nm,the amount of phase modulation obtained is basically robust,and the effect of size change on the modulation is negligible,which provides the basis for the flexible preparation of the device.The experimental results of different grating parameters on the phase modulation are studied,and a large number of data can be obtained for the preparation of real devices.