Enhancement of modal birefringence in solid core Bragg fibers with high-index-contrast claddings

Abstract

Abstract We present two types of highly birefringent solid core Bragg fibers (SCBFs) with high-index-contrast claddings by asymmetrically introducing low index parts (LIPs) into the solid core. The characteristics of their modal birefringence and confinement loss are numerically investigated by using a full-vector finite element method. The simulation results reveal that the modal birefringences in such highly birefringent SCBFs essentially depend not only on the difference in electric field boundary condition between the orthogonal-polarized modes, but also on the photonic bandgap effect. Both types of highly birefringent SCBFs have higher modal birefringence than those with low-index-contrast claddings, owing to the large refractive index (RI) modulation ranges of the LIPs. The modal birefringence of the fundamental mode at the targeted 1550 nm is strongly dependent on the size, RI and location of LIPs. Notably, the linear relationship between the modal birefringence and the RI of LIPs in the y-direction in a highly birefringent SCBF with four LIPs included can serve as a new sensing mechanism for the RI measurement of liquid analytes. We believe that the results would be beneficial to the design and application of highly birefringent SCBFs with high-index-contrast claddings.