Ge20Sb15Se65 glass-based ultra-bandwidth X-shaped dual-core photonic crystal fiber polarization beam splitter with an air hole filled gold rod

In this paper, a novel X-shaped dual-core photonic crystal fiber polarization beam splitter (X-DC-PCF PBS) with an air hole filled gold rod based on Ge20Sb15Se65 glass is proposed. According to the DC mode coupling theory and surface plasmon resonance effect, the mode coupling phenomena of the 𝑥 polarization (X-pol) and 𝑦 polarization (Y-pol) odd and even modes are analyzed, respectively. The variation laws of coupling lengths of the X-pol and Y-pol and the coupling length ratio with different structural parameters at wavelength 1.55 µm are investigated. When the shortest polarization splitting length (𝐿PS) is 230 µm, there is only the X-pol and Y-pol light in the cores A and B, respectively. By considering the variation of the extinction ratio and insertion loss (IL) with wavelength, the final polarization splitting bandwidth (PSB) is 358 nm (1.367–1.725 µm), and the maximum ILs of the X-pol and Y-pol in the whole PSB are 0.04 and 0.8 dB, respectively. The proposed X-DC-PCF PBS has ultra-wide PSB, short 𝐿PS, and ultra-low IL, so it will play an important role in the development of optical integration technology and the construction of an all-fiber loop platform.