High birefringence, single-polarization, low loss hollow-core anti-resonant fibers.

We present a novel hollow-core anti-resonant fiber (HC-ARF) with a cladding ring, two nested resonant tubes and two nested silicon tubes. The cladding ring in the fiber contributes to decrease the fundamental mode (FM) loss of x-polarization and enlarge the polarization-extinction ratio (PER). In addition, the nested silicon tubes can improve birefringence greatly. The combination of cladding ring, nested resonant tubes and nested silicon tubes can make the fiber obtain low FM loss, single-polarization, and high birefringence. Specifically, the proposed HC-ARF exhibits total FM loss of x-polarization, PER, and birefringence of 0.89 dB/km, 4432, 3.07×10, respectively, at 1.55 µm. Moreover, the y-bend direction has a great influence on the propagation properties of the fiber. The fiber in the x-bend direction has low total bend-loss of 0.004 dB/m for a small bend radius of 5.8 cm.