A low loss and high birefringence suspended hollow-core THz fiber

High birefringence fibers is effective for polarization maintaining sensing and high rate communication applications. Recently, high birefringence fibers for Terahertz (THz) waves have also been desired to improve qualities of polarization sensitive THz time-domain spectroscopy. In this paper, we will introduce a kind of index-guiding suspended hollow-core high birefringence THz fiber. Two rectangular shaped dielectric strips extend in the x- and y-orientations, respectively. The orthogonal sector of the strips in the x- and y-orientations acts as the fiber core. The rest of these rectangular shaped strips, four big air holes and the dielectric cirque constitute the cladding of the fiber. The main function of the dielectric cirque is fixing the strips. The two dielectric strips in the x-orientation have the same thickness with each other, and the case is similar for the strips in y-orientation. By simply adopting dielectric strips distributing in the two directions with different thicknesses, a high birefringence up to 10
⁻²
level can be achieved over a wide frequency range from 0.7 ∼ 1.3 THz. Due to the suspended hollow core of the fiber, most fraction of the THz field energy propagates in the air region, which can efficiently reduce the loss caused by the absorption of the fiber material. Compared with the rectangular-shaped porous fibers reported before, this fiber proposed here has the similar birefringence while much lower propagation losses. Additionally, the outer dielectric cirque effectively isolates the fiber from the surrounding environment, which guarantees any contact on the surface of this fiber not disturbing the field and inducing additional losses.