Ultra-broadband dual hollow-core anti-resonant fiber polarization splitter

Abstract A dual hollow-core anti-resonant fiber is proposed and numerically investigated. Two elliptical tubes are introduced to separate the core into two symmetrical cores; further nested tubes are adopted to achieve good single mode performance. Mode coupling takes place in the proposed fiber through an air gap between the two cores; the coupling strength can be controlled by adjusting fiber parameters. A broadband polarization splitter can be constructed by selecting a suitable fiber length. Numerical results show that a polarization splitter based on the proposed fiber has a length of 6.75 cm and a bandwidth of 310 nm, covering the wavelength range from 1.41 μm to 1.72 μm with an extinction ratio as low as −20 dB. The ratio of higher order mode to fundamental mode loss is great than 100, implying that the proposed polarization splitter also possesses effective single mode performance.