Ultrawide bandwidth single-mode polarization beam splitter based on dual-hollow-core antiresonant fiber.

An ultrawide bandwidth and single-mode polarization beam splitter (PBS) based on an air-gap type of dual-hollow-core antiresonant fiber (DHC-ARF) is proposed. Nested tubes are introduced into two cladding tubes between two cores to weaken the wavelength dependence of coupling length in DHC-ARF for obtaining ultrawide bandwidth. By tuning the cladding tube sizes, higher-order core modes with the lowest loss can be coupled with cladding tube modes, and thus, effectively, single-mode operation is achieved. Numerical results demonstrate that an 8.15 cm long DHC-ARF can be used to develop a PBS with an operating bandwidth of 370 nm ranging from 1.28 to 1.65 µm, where a polarization extinction ratio is below -20 and a high-order mode extinction ratio exceeds 100.