Anti-resonant hollow-core fiber with highly birefringent meniscoid nested structure

In this paper, we propose a meniscoid nested anti-resonant hollow-core fiber (MAF), wherein the fourfold rotational symmetry structure enables high birefringence and low loss in dual-wavelength range. The bi-thickness structure lies in orthogonal directions, disrupting the symmetry of the cladding and introducing high birefringence. The relationship between MAF cladding tube’s wall thickness, rotational symmetry, and birefringence is revealed. Compared to traditional fiber structures with the same parameters, the proposed structure exhibits lower confinement loss (CL) and higher birefringence. The trade-off between birefringence and CL is further analyzed. Consequently, MAF breaks the original symmetry of the circular cladding structure, inducing an effective refractive index mismatch that results in birefringence exceeding 10^-5 across O and C band. The MAF possesses a birefringence of 1.8×10^-5 at the O band and 1.1×10^-4 at the C band. These results indicate that the proposed MAF has great potential for polarization control, polarization imaging, and fiber gyroscope applications.