Dual-core PCF-based THz polarization beam splitter with broad bandwidth and ultra-high extinction ratio

A new terahertz (THz) polarization beam splitter (PBS) based on cyclic olefin copolymer (COC) photonic crystal fiber (PCF) with a simple structure is proposed. The dual cores are achieved by introducing six circular air holes in two rows of upper and lower symmetry into the fiber core. The mode coupling characteristics between the even and odd modes for the proposed dual-core PBS are investigated using the time-domain finite-difference (FDTD) method and coupled-mode theory. The influence of geometrical structure parameters on the PBS performance is analyzed. The numerical simulation results reveal that when the incident light frequency is 0.6 THz and the PBS length is 53.88 mm, the bandwidths of 0.0217 THz (from 0.5895 THz to 0.6112 THz) and 0.0225 THz (from 0.5908 THz to 0.6133 THz) are obtained for the x and y-polarization modes, respectively. The highest polarization extinction ratios (ERs) are 114.5 dB and 72.3 dB for the x and y-polarization modes, respectively. The simple structure and wide bandwidth make the proposed PBS will find extensive applications in THz communication, imaging, sensing, metrology, and microscopy.