Slot Spiral Silicon Photonic Crystal Fiber With Property of Both High Birefringence and High Nonlinearity

A photonic crystal fiber (PCF) made of silicon is proposed and numerically optimized with both ultrahigh birefringence and nonlinearity. By introducing an elliptical low-index slot in the core region, one of the orthogonally polarized fundamental modes can be confined in the low-index region due to the discontinuity of its electric field at the interface of the slot and the surrounding material, while the other fundamental mode is dominated by the modified total internal reflection (MTIR) induced by air holes of the cladding, leading to a birefringence as high as 10^-1 order. On the other hand, benefiting from the tight field confinement and highly nonlinear material, nonlinear coefficients up to 1068 W^-1 · m^-1 and 162 W^-1 · m^-1 can be achieved for the slot mode and the MTIR mode, respectively.