Design of a broadband dual-cladding PCF polarization filter via triple surface plasmon resonance effects

Abstract

Photonic crystal fiber (PCF) polarization filters are widely utilized due to high integrity and flexible tunability. However, most filters still face the challenges from intricate structure and limited bandwidth. Here, we propose a dual-cladding PCF polarization filter with a large bandwidth by triple surface plasmon resonance (SPR) effects. Asymmetric Au-filled air holes are arranged in the dual-cladding lattice to excite the triple SPR effects with enhanced birefringence, therefore extending the operating bandwidth. The results show that the triple SPR phenomena occur in the y-polarized direction at resonance wavelengths of 1212.8, 1347.5, and 1567 nm with confinement losses of 946.63, 826.79, and 737.13 dB/cm, respectively. In contrast, the x-polarized direction shows extremely low confinement losses of only 0.20, 1.94, and 2.03 dB/cm. With the fiber length (L) of only 300μm, the filter achieves the maximum crosstalk (CT) of 246.62 dB, and the bandwidth above 20 dB extends to 830 nm. High performance filter based on multiple SPR effects may has the potential applications in optical communication and optical sensing.