摘要： A waveplate, well known as a phase retarder, manipulates the polarization state of incident light travelling through it and is a necessary component in many optical systems. Generally, waveplates are constructed out of birefringent materials which lead to the different phase retardation of incident light according to initial polarization state. For the terahertz (THz) spectral range, however, there are some limitations including thickness, transmission, and cost for the waveplate fabrication due to the lack of natural materials that possess strong birefringence in this region. Recently, THz waveplates based on metasurfaces have been proposed to overcome this limitation. Single-layered metasurfaces have been utilized as THz quarter-waveplates (QWPs), for which a retarded phase of 90 degrees is sufficient. [1]. To achieve phase retardation of 180 degrees and realize THz half-waveplates (HWP), stacked single-layered metasurfaces have been adopted [2], but this approach requires sophisticated fabrication processes and sacrifices structural simplicity. In this work, we propose a relatively simple single-layered metasurfaces that make possible to induce phase retardation of up to 90 and 180 degrees with a tunable operation frequency. The metasurfaces consist of rectangular ring resonators which are strongly coupled with each other and separated by a deep-wavelength gap, giving the metasurface an extraordinarily high anisotropic effective permittivity [3]. The x and y components of the effective permittivity of metasurface are closely associated with the gap widths of gx and gy along the x and y axes, respectively. The metasurface possesses strong birefringence when gx and gy are different and acts as the HWP and QWP at certain conditions depending on the operation frequency. To experimentally demonstrate the feasibility of the proposed metasurfaces, we optimized rectangular ring resonator size and gap width through Finite-Difference Time-Domain simulation and fabricated the metasurface on stretchable PDMS film for mechanical deformation. Subsequently, we confirmed the efficient performance of our single-layered metasurface as the THz HWP and QWP together with its spectral tunability through mechanical deformation of the metasurface by THz spectroscopy.