Mid-infrared silicon photonic crystal fiber polarization filter based on surface plasmon resonance effect

In this paper, a novel silicon photonic crystal fiber (Si-PCF) polarization filter based on surface plasmon resonance effect is proposed for the first time. With the full-vector finite-element method, the mode coupling characteristics of the Si-PCF with the gold-coated film between the core mode and surface plasmon polariton mode are investigated, and the confinement losses are analyzed. The confinement losses of the Y-polarized core mode at the three resonant wavelengths 2.84, 3.29, and 4.53μm are 9235.9, 27097.5, and 97818.3 dB/m, respectively. The extinction ratio reaches -391 dB and the insertion loss is less than 1 dB when the Si-PCF length is 4 mm, along with the filter bandwidth of 2.75μm. Moreover, by modifying the fiber structure parameters, the filter bandwidth of the proposed three kinds of Si-PCF polarization filters can cover 2.75 to 7.80μm. It is believed that the proposed Si-PCF polarization filter has important applications in the mid-infrared laser and optical communication systems.