Wide-bandwidth mode converter based on a dual-hollow-core anti-resonant fiber

Abstract

This paper proposes a broadband mode converter utilizing a dual-hollow-core anti-resonant fiber (DHC-ARF) for the first time, in which the mode index matching between LP01 and LP11 modes is achieved by adjusting the core diameter size of the hollow-core anti-resonant fiber (HC-ARF). Notably, the air gap can become the main channel for the energy exchange between the two cores by adjusting the air gap size between the two cores of the DHC-ARF. The coupling length of the mode converter is greatly reduced, and a compact and broadband mode converter is realized. Simulation results demonstrate that the proposed mode converter achieves a coupling efficiency (CE) of 92.79 % at a wavelength of 1.55 μm at a length of 10.7 mm. The bandwidth of 330 nm at a CE greater than 90 % covers the E + S + C + L + U bands. The proposed mode converter exhibits a large core diameter compatible with hollow-core fiber communication and is expected to be applied for high-speed and high-capacity hollow-core mode-division-multiplexing fiber-optic communication. The device design methodology presented in this paper can also provide technical references for developing higher-order mode converters, such as LP01 mode to LP02 mode and LP01 mode to LP21 mode, based on DHC-ARF.