Broadband Single-Polarization Operation in Square-Lattice Photonic Crystal Fibers

A broadband single-polarization single-mode optical fiber is proposed. One of the polarized states of the highly birefringent square-lattice photonic crystal fiber is eliminated by index-matched coupling with the modes of two cladding defects. Numerical results show that single-polarization operation with the transmission losses of one polarized state larger than 2 dB/m and the losses of another state lower than 2 dB/km can be realized in a spectral region ranged from 1477 to 1776 nm. In addition, by modifying the air holes surrounding the cladding defects, the losses of the unwanted polarized state can be enhanced to be larger than 10 dB/m, with the losses of the transmission state lower than 0.1 dB/m in a 560-nm-broad spectral region.