Semi-Empirical Model for Calculating Birefringence and Confinement Loss in Bi-Thickness Fourfold Anti-Resonant Hollow-Core Fiber

We provide a semi-empirical model for straightforward and rapid evaluation of the effective index, confinement loss and birefringence of mainstream birefringent anti-resonant hollow-core fibers (Bi-ARFs). It is based on the observation that the polarization-dependent performance of Bi-ARF shows a weak reliance on the order or type of anti-resonant band. The comparison with the simulation results validates the effectiveness of this model. Furthermore, the model provides an optimal bi-thickness selection strategy to maximize birefringence while minimizing loss penalty. We believe that this model offers physical insight of the birefringence mechanism in ARFs and can accelerate the development of high-performance BI-ARFs for polarization-sensitive applications.