Broadband terahertz polarization converter with anomalous reflection based on phase gradient metasurface

In order to expand the application situation of the polarization converter in terahertz band, a broadband polarization converter based on phase gradient metasurface is proposed for simultaneously manipulating the polarization and the wavefront of the reflected wave in terahertz region. Consisting of six different “H”-shaped resonators which can tune the phase and the polarization respectively, the polarization converter is able to deflect the normally incident terahertz wave with an anomalous reflection angle while changing the polarization. Geometric rotation and resonant frequency modulation constitute the phase variation of the unit, which can be superimposed on each other without interference. The simulation results show that the reflecting angle from 0.40 to 0.60 THz varies from 39° to 22° with side lobe level lower than −14 dB. Specific elucidation for high polarization conversion ratio is discussed through reflection phase and resonant branch analysis. Compared to the conventional polarization converter, the proposed one has an advantage in propagation manipulating, which reveals its potential application in THz detection, imaging and sensing, etc.