Compared with using the light interference of two actual beams to obtain holograms, computed holography has the advantages of low noise, simple operation, high repeatability, and holographic reproduction of virtual objects. Meanwhile, computer-generated holography technology is commonly used to reconstruct arbitrary images and is widely used in virtual reality, advertising and anti-counterfeiting systems. Terahertz wave refers to the electromagnetic wave between 0.1 THz similar to 10 THz, between millimeter wave and far infrared wave. The unique spectral position of terahertz waves gives it the advantages of low photon energy, rich spectral information, strong penetration ability, and large bandwidth. Based on the above characteristics, terahertz holographic technology is widely used in biomedical imaging, safety screening, non-destructive testing, and evaluation fields. However, limited by the inherent refractive index of natural materials, traditional propagation and reflective terahertz functional devices are usually composed of High-density Polyethylene(HDPE), Polytetrafluoroethylene(PTFE), Polymethylpentene(TPX), quartz and sapphire, which inevitably leads to their large size, heavy weight and low efficiency, which hinders the development of miniaturization and integration of terahertz systems. Metasurface refers to a two-dimensional array of sub-wavelength artificial unit structures arranged on a plane. It can flexibly adjust the wavefront amplitude, phase, polarization, and orbital angular momentum through ease of integration and manufacturing, with the potential to control electromagnetic waves flexibly. It retains the advantages of electromagnetic regulation of three-dimensional metamaterials, and its preparation difficulty and propagation loss are significantly reduced due to its planar structure characteristics. The design of a suitable metasurface element structure can afford the capability to modulate the optical field flexibly, thereby enabling the realization of diverse functionalities, such as beam focusing, beam diffraction, generation of specialized beams, beam shaping, and holographic image reconstruction. Based on the above research background, this paper uses the GS algorithm to obtain the optimal solution distribution of the target object's phase. Then it uses the all-silicon rectangular column as the basic unit structure to arrange metasurface-regulated terahertz waves to achieve holographic imaging. This research proposes a new type of meta-atom structure, the all-silicon rectangular column, as the fundamental building block for the terahertz metasurface. This design overcomes the drawbacks of traditional metal-based metasurfaces, such as high ohmic losses and low polarization conversion efficiency, by implementing Mie-type electrical resonance and magnetic resonance or an effective waveguide effect. These phenomena result in the modulation of wavefronts at terahertz frequencies. Different phase regulation methods are used to design metasurfaces to achieve holographic imaging with different functions. Metasurfaces based on geometric phase control can realize holographic imaging and verify that the obtained image has a specific broadband. On this basis, the rational design of the metasurface element structure realizes a circular-bias multiplexing function based on the simultaneous regulation of the geometric phase and propagation phase. The specific function realized is to obtain holographic images of the letter E when right-handed circularly polarized light is incident light. When left-handed circular polarized light is incident, a hologram of the letter F is obtained. Compared with the holographic diffraction efficiency obtained by using metasurfaces made of metal, the diffraction efficiency of holograms can be effectively improved by using the all-silicon column structure. To a certain extent, this design solves the shortcomings of considerable size, heavy weight and low efficiency of traditional functional devices in the terahertz band and promotes the development of integrated and multifunctional terahertz technology in the terahertz band. It shows excellent potential for holographic imaging and wavefront regulation applications. The polarization multiplexed holographic imaging proposed in this paper can store multiple pieces of information in one carrier, set the incident light in different polarization states to obtain different information, and present different holograms. The implementation of this approach utilizing the metasurface can result in the enhancement of multi-channel holographic imaging, thereby significantly increasing the utilization efficiency of the metasurface technology. This not only has significant potential in terms of large-scale information storage but also has potential applications in polarized optics and holographic data encryption.
