Ultra-broadband small-size dual-core photonic crystal fiber polarization splitter based on silver coating

We have proposed a novel silver-coated ultra-broadband small-size dual-core photonic crystal fiber (DC-PCF) polarization splitter which achieves a short length, high extinction ratio (ER) and ultra-wide bandwidth at the commonly used communication wavelength band. Finite element method-based numerical simulation is applied to carry out a thorough investigation for wavelength from 1 to 2 mu m. According to the simulation results, the coupling qualities of the proposed structure can be improved by resonant coupling between the core guide mode and the surface plasmon polarization (SPP) exciton mode. By analyzing the change of ER with varying wavelength, the ER value of this work are achieved as 67.4 and 67.1 dB when the wavelength are 1.14 and 1.57 mu m, respectively. The final splitting length (LS) is 17.17 mu m. To the best of our knowledge, it is difficult to achieve in all previous studies. With a splitting bandwidth of 900 nm (1.0-1.9 mu m) and the ER value of -50.1 dB at 1.55 mu m, the E + S + C + L + U communication bands are completely covered. The proposed model has excellent beamsplitting performance, such as ultra-short LS, ultra-wide splitting bandwidth and good tolerance performance, with potential applications in optical fiber communications or fiber laser devices.