| With the improvement of semiconductor fabrication technology,micro / nano tunable devices with integration and miniaturization have gradually entered the vision of scientific researchers and been widely concerned,such as the metasurface used in optical imaging and regulating the optical wave transmission performance,and the multi-layer film devices with uncomplex fabrication process.However,due to the variety of natural materials and the complexity of structure,all kinds of functional modulators that can be applied in practice are still scarce.Therefore,it is a very important task to develop flexible and adjustable devices that can adapt to more scenes and achieve more functions.In this paper,three kinds of optical devices are designed and studied on the basis of metal/dielectric multilayer structure by comparing theoretical simulation with experimental test,and according to the conventional operating band and optical characteristics of the device:A MIM structured metalens is proposed,which consists of a square metal ring,a silicon substrate and a gold grating.Under the condition of fixed incidence of terahertz wave,the transmission phase can be further adjusted by adjusting the structural parameters of the square ring in the unit cell,including the ring side length,opening size and direction,the transmission intensity can be kept constant,simultaneously,so that the 12 units of the metalens array can be selected.The unit cell can be regarded as a Fabry-Perot-like resonator,which can not only filter the cross polarized light to be studied by the grating layer,but also enhance the optical wave transmission performance.On this basis,according to the focusing characteristics of the lens and the concept of split phase mode,one-dimensional chain and two-dimensional plane metalenses are designed successively,and the corresponding single spot and multi-spot focusing effects are simulated by electromagnetic field simulation software.A reflective phase holographic metasurface composed of square metal ring,metal reflector,rigid(silicon)or flexible(PMMA)substrate is proposed.Under the condition of fixed millimeter wave incidence,firstly,the units with fixed amplitude and reflection phase of cross polarized light covered 0-2? are selected through simulation calculation,and the coupling effect between adjacent units is further analyzed in combination with the change of unit period,so as to ensure the minimum interference of the selected units in the formation of metasurface array.Next,the phase recovery of the hologram is realized by using GS algorithm and RS numerical integration method combined with the preset target image,and the hologram formed by cross polarized light is scanned in the millimeter wave experimental optical equipment.Finally,considering the influence of the number of metasurface arrays on the imaging quality,a large area of flexible holographic metasurface is fabricated by wet etching method,and the hologram is successfully obtained.A nearly perfect absorber composed of antireflective AR coating,MIM resonator,silicon or PMMA substrate,MIM resonator and AR coating is proposed,which based on transversely symmetrical structurecan and can achieve ultrabroadband absorption in the band of400-2500 nm with an average absorption rate of 93%.Firstly,the parameters of the absorber were designed and optimized by the FEM simulation software and the film design software,and the samples were successfully fabricated.Then the refractive index range of the absorbing metal layer is analyzed theoretically to determine the absorbing metal Cr.Then,the influence of each coating on the absorption properties is studied by means of the theory of thin film transmission matrix and the method of optical admittance loci.In addition,the absorber is insensitive to polarized light in the range of 60 ° incident angle.Finally,it is found that the flexible absorber based on PMMA can still maintain high absorption performance under the condition of large angle bending deformation. |
PDF Full Text Request