Design and simulation comparison of terahertz surface wave based on grating coupling method

In the THz band, the spoof surface plasmon polariton (SSP) can limit the light to the designed specific spatial frequency by constructing a sub-wavelength structure on the metal surface. This ability makes it possible to break through the diffraction limit of THz imaging. In this paper, a one-dimensional metal groove structure is used to generate the SSP, and the frequency shift characteristics of the object's spatial spectrum under the excitation of a 2.52 THz beam are analyzed. On this basis, a grating-coupling-based SSP excitation structure is designed, which consists of a combined array of subwavelength metal grooves and subwavelength slits with different periods. This structure is used to generate strong intensity and make full use of the incident beam. It is promising for generating illumination beams for terahertz far-field super-resolution imaging of subwavelength-spacing samples.