In this study, a design for the high-efficiency transmissive terahertz polarization beam splitter is proposed. Based on the metal–insulator–metal waveguide array structure, it is found that the phase change between the transverse-electric (TE) and transverse-magnetic (TM) modes of terahertz wave transmission depends greatly on the medium width. According to this phenomenon, our designed devices can achieve polarization splitting of TE and TM modes in the frequency range 0.8–2.4 THz, and the transmittance can be maintained above 85%. In addition, through judicious design, polarization splittings with 93% transmittance at 1 THz and 95% transmittance at 1.5 THz are obtained, and polarization splitting at different angles is achieved according to variable periods. Compared with the traditional polarization beam splitter, this design has the advantages of adjustable frequency, high efficiency, and easy integration, thus having potential application in terahertz optical systems.
