Broadband Single-Polarization Single-Mode Operation in Highly Birefringent Photonic Crystal Fiber with a Depressed-Index Core

A novel design for a broadband single-polarization single-mode photonic crystal fibers is proposed and numerically analyzed by using a finite-element method. It is shown that the single-polarization single-mode operation spectral region of a highly birefringent photonic crystal fiber can be strongly enhanced by introducing a suitably down-doped silica rod inside the fiber core. In the proposed design, the single-polarization single-mode guidance can be realized in the wavelength range from 1.0 to 1.8 µm with the confinement loss less than 0.12 dB/km.