Design of short-length polarization beam splitter based on highly birefringent dual-core photonic crystal fiber

We propose an all circular-air-hole short-length polarization beam splitter (PBS) with high extinction ratio based on dual-core highly birefringent photonic crystal fiber (PCF). The impacts of geometrical parameters on the coupling polarization dependence, coupling length ratio (CLR), and propagation property are numerically investigated by the full-vector finite element method (FEM) and the semi-vector beam propagation method (BPM). From simulation results, it is seen that CLRs at the excitation wavelength of 1.55 μm can be optimized to be closed to the desired values of 3/2 and 4/3 to satisfy the sufficient condition of splitting polarized modes by appropriately tailoring the air-hole sizes. For the two optimal structures, the separation of x- and y-polarized modes can be achieved in short lengths of 1.41mm and 2.89mm at the operating wavelength of 1.55 μm, respectively. Furthermore, the extinction ratios at λ = 1.55 μm are estimated to be 97.7 dB and 88.1 dB, and the wavelength bandwidths of extinction ratio better than 15 dB are about 107 and 82 nm, respectively.