Research Of Meta-Holography At Terahertz Frequencies

Consisting of two-dimensional subwavelength meta-atoms,metasurfaces are capable of even arbitrarily engineering the electromagnetic(EM)waves,delivering new possibilities for holography.In this dissertation,the superior properties of metaholography over the conventional computer-generated holography(CGH)are revealed in terms of the differences in design,materials,and performances.The works are mainly demonstrated at terahertz frequencies,including:1.Different from the phase-only or amplitude-only hologram design applied in the conventional CGH,simultaneous multi-level phase and amplitude modulation method is employed directly,leading to high-quality and low-noise holographic imaging.Such technique can reconstruct both the phase and the amplitude information of the virtual image,by which continuous shifting,stretching,and rotating of the holographic images can be achieved along the propagation direction of EM waves.2.By introducing the planar chiral structures that only contribute under a certain circular polarization,meta-holography multiplexing is achieved based on circular polarizations.Attempting to realize full control or utilization over all the four fundamental properties of EM waves,meta-holography multiplexing under two different linear polarizations and two different frequencies is demonstrated finally.3.By combining phase-change materials with plasmonic metasurfaces and elaborately designing and distributing two different types of structures,both the phase and amplitude of the virtual images can be reconstructed by simultaneous phase and amplitude control over the meta-hologram,resulting in realization of thermallydependent dynamic meta-holography.4.By adopting the methodology used in metasurface technology and holography,terahertz meta-lens array and metasurface fisheye lens working in the visible region have been achieved respectively.Compared with the conventional counterparts,our scheme is much more compact,smaller,and lighter,which solves the problems of the current conventional lenses including bulky and hard to be integrated.