of applications. Spatial light modulators, which can impose programmable modification of the spatial intensity and/or phase distribution of an optical beam, are commonly used in applications, such as optical information processing, imaging, and communications. However, in the THz frequency range, the development of spatial light modulators remains a great challenge due to the lack of electrooptical materials, although they are urgently requested with the ongoing advancement of THz technology and the identification of a variety of potential applications. [5] While a few spatial THz intensity modulators have already been proposed, [6][7][8][9] a pure phase spatial modulation can greatly increase the immunity to noise, therefore is more robust and applicable in THz systems where the intensity of THz radiation is typically low. Steinbusch et al. used the photogenerated graded index grating to actively steer the THz beam; the phase modulation was considered. [10] However, the phase modulation is caused by the change of reflection index of the thin semiconductor film pumped by the visible light, which is quite small. Other attempts used semiconductor quantum well structures at cryogenic temperatures and liquid crystals with low modulation speed. [11,12] More recently, metamaterials/ metasurfaces integrated with semiconductor and graphene have allowed more efficient modulation of THz phase. [13,14] However, the range of THz phase modulation needs further improvement, and one should also address the drawback of accompanied intensity modulation associated with the resonant response.Despite these limitations to overcome, the emergence of metasurfaces has provided an excellent opportunity to accomplish a variety of functional THz devices. [15][16][17] Metasurfaces are constructed from carefully designed discrete metallic or dielectric elements and have spatially varying characteristics across its surface, [18] enabling effective manipulation of the amplitude, phase, and polarization state of electromagnetic waves with continuously broadband achromatism for ultrathin planar lenses, [19,20] complex light field generation, [21] spin orbital angular momentum coupling, [22,23] and metasurface holograms. [24,25] Activating these functionalities will no doubt expand the application scope and create a greater societal impact of metasurfaces, which necessitates the integration of functional materials within the metasurface structures, including most widely used semiconductors, phase transition materials, and Terahertz (THz) radiation has many potential applications. However, comparing with the rapid development of THz sources and detectors, functional devices for THz modulation, especially the spatial modulation devices, are still insufficient. Here, a novel approach for generating arbitrary wavefronts of a THz beam is presented. By dynamically creating metasurface structures through illuminating a thin silicon wafer with femtosecond laser, which is spatially modulated, an array of reconfigurable subwavelength resonators is generate...

Metasurface provides subwavelength structures for manipulating wavefronts of light. The benefits of subwavelength components offer a continuous modulation of amplitude, phase, and polarization, thus eliminating the production of higher-order images and improving the utilization of light intensity. Despite the rapid progress in this field, multiparameter control of light using single layer metasurface is rarely reported. In fact, multiparameter control of light helps to improve information storage capacity and image fidelity. With simultaneous manipulation of polarization and amplitude at each pixel, it is possible to encode two separate images into one metasurface and reconstruct them under proper conditions. In a proof of concept experiment, we demonstrate an independent display of two binary images at the same position with polarization de-multiplexing from a single metasurface. This unique technology of encoding two images through amplitude and polarization manipulation provides a new opportunity for various applications in, such as encryption, information storage, polarization holograms, optical communications and fundamental physics.