Ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber

An ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber is proposed. Two fluorine-doped cores and a central microstructured modulation core are introduced to achieve an excellent performance and an ultrawide bandwidth. Numerical simulation demonstrates that the splitter has a bandwidth as wide as 300 nm, with an extinction ratio (ER) as low as -20  dB. At the wavelength of 1.55 μm, the ER reaches -30  dB. All the air holes in our design are circular holes and are arranged in a triangular lattice that is easy to fabricate with the method of stack and draw. A suitable mode field area and a Gaussian-like mode field distribution lead to a low splicing loss that is as low as 0.04 dB when splicing with standard single-mode fibers as the lead-in and lead-out ports.