Wavelength-Switchable Polarization Filter Based on Graphene-Coated D-Shaped Photonic Crystal Fiber

A wavelength-switchable polarization mode filter (PMF) based on a graphene-coated D-shaped photonic crystal fiber (DPCF) is proposed. Due to the different coupling properties between the two polarized core modes and surface plasmon polariton (SPP) modes, the PMF is designed for y -polarized mode filtering. In order to enhance the interaction between the graphene and fiber, gold is coated on top of graphene. Finite element method is applied to analyze the performance. Results show that the filtering wavelength can be modulated by adjusting the chemical potential ( μ c ) of graphene. Especially, a single-wavelength PMF can be switched to a dual-wavelength or a three-wavelength filter by increasing the value of μ c . The extinction ratio is higher than 25 dB with a small device length of 100 μm over the wavelength range of 1.0~1.4 μm. The wavelength-switchable PMF has a great potential in polarization modulation, WDM communication system, and multi-parameter sensing.