Polarizing photonic crystal fiber with low index inclusion in the core

We demonstrate that adding a boron-doped inclusion in the core of a polarizing photonic crystal fiber significantly increases its polarization bandwidth. We present the characteristics of two fabricated fibers, including spectral dependence of loss in both polarization modes and polarization-dependent loss in straight as well as bent fibers. Our experiments prove that bending significantly increases the polarization band of the boron-doped fibers on the short wavelength edge. For a properly adjusted bending radius a single polarization guidance can be obtained in a wide spectral range. Moreover, we present the results of loss simulations carried out for the actual geometry of the fabricated fibers, which are in agreement with the measurement results