A photonic quasi-crystal fiber composed of circular air holes with high birefringence and low confinement loss

A photonic quasi-crystal fiber (PQF) consisting of Ge₂₀Sb₁₅Se₆₅ and all circular air holes exhibits high birefringence and low confinement loss(CL). The design which incorporates a simple eight-fold Penrose photonic quasi-crystal structure and six symmetrical circular air holes around the core is analyzed and optimized numerically using the full-vector finite element method by adopting the perfectly matched layer boundary condition. The maximum birefringence of 1.33 × 10⁻¹ is achieved at 1.55 μm and CLs of the X-polarization and Y-polarization modes are less than 10⁻³ and 10⁻⁶ dB/m, respectively, in the wavelength range between 1.41 and 1.69 μm. To the best of our knowledge, this structure shows the highest birefringence among PQFs with all circular holes reported so far and has great potential in high-performance optical devices.