Hollow-Core Anti-Resonant Fiber with Dual-Geometry Cladding for Mid-IR Transmission

We introduced and theoretically assessed a new hollow-core anti-resonant fiber (HC-ARF) with dual geometry cladding structure, suited for high power $2 \mu m$ laser trans-mission. The fiber uses nested dual-layer circular and elliptical tubes to provide low-loss single-mode $(LP_{01})$ transmission. We optimized the finite element method (FEM) to produce a loss of less than $1.5 \times 10^{-2}dB/m$ between $1900 - 2100 nm$ with a remarkable low loss of 1.9×10⁻³ dB/m at 2025 $nm$. The concept achieves a high-order mode extinction ratio (HOMER) of over 1800 across a wide bandwidth. Furthermore, the fiber has exceptional bending tolerance, with a loss of $5.6\times 10^{-3}$ dB/m. at 1960 $nm$ at bending radii above 17 cm. These findings demonstrate the HC-ARF's exceptional potential for efficient 2 µm. laser transmission.