Compact terahertz wave polarization beam splitter based on self-collimating photonic crystals

In this article, a compact terahertz wave polarization beam splitter is proposed for terahertz systems. The design is based on the self-collimation effect in two-dimensional photonic crystals. A ring-type photonic crystal which consists of air rings in silicon background is employed in the design to get a broader bandwidth. The self-collimation for both TE and TM mode is achieved by manipulating both the outer and the inner radii of the rings. A defect region is embedded into the photonic crystal to separate the TE- and TM-polarized wave. The proposed polarization beam splitter has a very compact size of 659 μm × 659 μm. The plane wave expansion method is used to obtain the equi-frequency contours and the band diagrams. The finite-difference time-domain method is used to simulate the light propagation in the structure. The polarization extinction ratio of about 36.23 dB for TM-polarized wave and 35.98 dB for TE-polarized wave are reported. The corresponding normalized transmissions at TM port and TE port are of about 92.87% and 93.15%, respectively. The impact of the incident angle on the polarization extinction ratio and normalized transmission are also studied.