Highly Birefringent Terahertz Waveguide Formed With Dual-Subwavelength Polymer Wires

We propose a highly birefringent terahertz (THz) waveguide, which is formed with two touching subwavelength polymer wires. The waveguide can provide a high modal birefringence larger than 0.01 over a wide frequency range, and a maximum birefringence up to 0.0525 is achieved when the waveguide is made of Topas. Different from other THz birefringent waveguides, a simple scaling rule exists for the proposed birefringent waveguide so that the waveguide can be designed easily for any desired operation frequency to obtain the maximum birefringence. Moreover, when the maximum birefringence takes place, a high coupling efficiency of 93%, a low absorption loss of 0.04 and 0.03 cm
^-1
for x- and y-polarizations, and a negligible bending loss are demonstrated in our simulations. Finally, the influence of material index is further examined. It is found that as the refractive index of the waveguide material increases, the magnitude of birefringence increases as well, while the frequency at which the maximum birefringence occurs will shift toward the lower region.