Spectral imaging of flexible terahertz coding metasurface

Applied Physics Letters, Volume 118, Issue 8, February 2021. Coding metasurfaces have emerged as a promising venue for terahertz (THz) beam steering and beamforming. In this study, we designed a transmission metasurface with a complementary structure based on Babinet's principle. The beam-steering capability of the coding metasurface is implemented by encoding “0” and “1” elements with different phase responses and by controlling the coding sequences. The deflection angle can be controlled by changing the period of these 0 and 1 elements. Despite the development of beam-steering technology, measurements of the direction pattern of steered THz beams remain challenging. Systems for THz time-domain spectroscopy and spectral imaging are used to characterize the flexible coding metasurfaces. The THz imaging system can provide information on the directional pattern of the beam. To verify the performance of the proposed metasurface, the experimental measurements of beam deflection were found to be consistent with the values yielded by a simulation. Our study provides an effective platform for the design and measurement of THz beam steering.