A high-birefringent photonic quasi-crystal fiber with two elliptical air holes

A photonic quasi-crystal fiber (PQF) with high birefringence based on ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) is described. There are two elliptical air holes in the core to increase birefringence and the outer air hole array has a twelve-fold Stampfli-type quasi-crystal structure. ZBLAN reduces absorption loss in the infrared region resulting in higher birefringence. The birefringence and confinement loss of the PQF are analyzed numerically by the full-vector finite element method. Birefringence is higher than that of conventional polarization-maintaining fibers due to the two elliptical air holes in the center and reaches the maximum of 4.15×10−2 at a wavelength of 2 μm. The novel structure has great potential in high-performance optical devices.