High birefringence and polarization-holding ability in nanosized optical fibers with Si bowtie cores

The focus of this study was mainly on the birefringence of nanosized bowtie-shaped slot core fibers that can transport ultrasmall optical spots. Here we showed large birefringence for the fibers reaching as high as 0.33, which is three orders of magnitude greater than normal-sized birefringent fibers, the main cause of which being the impact of geometrical birefringence arising from significant differences between the orthogonal modal distributions. Moreover, we investigated the polarization maintaining property for acute-angled bending in a 5-μm fiber and demonstrated slight degradations of less than 5 dB for the extinction ratio in a 180°bend, which was several orders of magnitude lower than the ratio for the fiber without bending. We used computer simulations for the estimates presented in this study. We believe that the high-polarization maintaining performance presented herein will be required for nanosized optical sensing probes and interconnections in photonic integrated circuits.