Investigation On Holographic Display Technology With Nanoaperture Array Metasurface

Computer-generated hologram(CGH),which can realize three-dimensional(3D)display of arbitrary object,is an ideal virtual reality(VR)technology.The energy efficiency,polarization response of the hologram,the clarity,diffraction angle and field of view(FOV)of the holographic image will be limited by the coding devices or materials.Metasurface is the two-dimensional(2D)version of artificial metamaterial,which can control the amplitude and phase of the electromagnetic wave through changing the orientation or dimension of the structure.The capability for controlling the electromagnetic wave in the sub-wavelength scale and the advantage for easy fabrication of the Metasurface make it an ideal coding material for CGH.There are plentiful reports about the Metasurface holography,such as broadband meta-hologram,colorful display,polarization switchable holography and dynamic holographic display etc.However,there are also some challenges,such as the expensive cost of processing,the poor quality of colorful holographic image,the limited FOV of the holographic image and the complex experimental setup for measuring the holographic image etc.Those factors restricted the development of the metasurface holography and impeded the practical application of the meta-hologram.In this thesis,we mainly investigate the above problems in the metasurface holography.The main works and results of this thesis are listed below:1.A metasurface hologram working in a broad wavelength range containing the whole visible and the near-infrared range is demonstrated by using the elongated nanoaperture.The tolerance to the fabrication errors,which include the orientation angle,length and width of the nanoaperture,the shape deformation,has been theoretically investigated.It indicates that the phase hologram is capable of tolerating 10% fabrication imperfection.Some other fabrication technologies can be used to fabricate the meta-hologram based on the property of processing tolerance.2.Based on the capability for controlling the electromagnetic wave in the deep-subwavelength scale,the off-axis illumination is proposed to increase the usable information capacity of the deep-subwavelength metasurface hologram.The imaging information capacity determined by the propagating wave field of the frequency spectrum is increased to 4 times,and the imaging information capacity determined by the distortion-free region is increased to 11.5 times,which is verified with experiment.The increase of the usable imaging information capacity through off-axis illumination for 3D hologram is also experimently proved with superimposition two holograms.3.A method to realize color holographic display by off-axis illumination is proposed.The relationship between the frequency spectrum shift and the incidence angle is explored and the color hologram is designed by controlling the frequency spectrum.The siginal-to-noise ratio(SNR)can be improved compared to other colorful holography using super-pixel by this method and a colorful image with SNR 126.3 is achieved in the experiment.4.A full space visible meta-hologram is proposed in consideration of the metasurface's polarization properties.Through investigating the influence of incident circular polarization and the change of the holographic image versus the hologram's phase,we proposed the full space visible meta-hologram.And a colorful holographic image is further achieved with off-axis illumination.5.The polarization multiplexed meta-hologram and polarization-independent metahologram are proposed.The multicolor holographic display and polarization encryption are simultaneously realized in the same polarization multiplexed metasurface sample.The output light modulated by the sample could form the same image with different polarization normally incident light,which can relieve the requirement on the incident polarization.