Ultra-large mode area microstructured core chalcogenide fiber design for mid-IR beam delivery

An all-solid large mode-area (LMA) chalcogenide-based microstructured core optical fiber (MCOF) is designed and proposed for high power handling in the mid-IR spectral regime, covering the entire second transparency window of the atmosphere (3-5 μm). The core of the proposed specialty fiber is composed of a few rings of high index rods arranged in a pattern of hexagon. Dependence of effective mode area on the pitch and radius of high index rods are studied. Ultra-high effective mode area up to 75,000 μm2 can be achieved over this specific wavelength range while retaining its single-mode characteristic. A negligible confinement loss along with a low dispersion slope (~0.03 ps/km-nm2), relatively low bend loss, and a good beam quality factor (M2~1.17) should make this LMA fiber design attractive for fabrication as a potential candidate suitable for high power, passive applications at the mid-IR wavelength regime.