Plasma dual-wavelength single polarizing filter with gold film and liquid-filled air hole based on photonic crystal fiber

A square structure of dual communication band single polarizing plasma photonic crystal fiber filter is presented in this paper. The resonance point can be adjusted to the communication band by optimizing the parameters of fiber structure. High birefringence can be produced by changing the refractive index of the filled liquid, the thickness of the metal film, and the diameter of the air holes near the core. Numerical simulation results demonstrate that the resonance strength of x- and y-polarized direction can simultaneously reach 781.87 and 463.04 dB cm−1 at the communication wavelength of 1.31 and 1.55 μm. By filling liquid analyte the confinement loss of x- and y-polarized direction can simultaneously reach 804.71 and 451.69 dB cm−1 at the wavelength of 1.31 and 1.55 μm. Furthermore, when the fiber length of L is equal to 700 μm, the peak value of the crosstalk can reach 474.63 and −243.61 dB at the same time at the wavelength of 1.31 and 1.55 μm, and when the length of the fiber L is 400 μm, the bandwidths of the crosstalk better than 20 dB and less than −20 dB are about 160 and 220 nm, respectively. These features make it an ideal candidate for the design of a dual band polarization filter device.