D-Shaped photonic crystal fiber with graphene coating for terahertz polarization filtering and sensing applications

•Graphene is used as the plasmonic material and surface plasmon resonance effect is obtained at the sub-terahertz frequency.•Operating frequency and bandwidth of the designed D-shaped Gr-PCF are dynamically tunable.•The designed D-shaped PCF can be used as polarization filter and biosensor in the sub-THz band. A D-shaped photonic crystal fiber with graphene coating on the polished flat surface is designed. Graphene is used as the plasmonic material and surface plasmon resonance (SPR) effect is obtained at the sub-terahertz frequency. Tunable loss spectra, polarization filtering and sensing properties are studied by using the finite element method. Tuning sensitivity of the SPR frequency is 595 GHz/eV. Bandwidth of 23.46 GHz centered at 0.48THz with crosstalk above 20 dB can be obtained when fiber length is 0.5 cm. The average wavelength sensitivity of 305.5 μm/RIU and the maximum amplitude sensitivity of 30.85RIU−1 are obtained for analyses with refractive index in the range of 1.3 to 1.4. Refractive index resolution of the order of 10−4 is predicted. The designed fiber can be used as terahertz polarization filter or biosensor.