Photonic crystal fiber with W-type effective refractive index profile

The concept of W-type photonic crystal fiber (PCF) was proposed in this paper. Using a full-vector finite element method (FEM), we simulated the promulgate loss property of a specific W-type PCF, which was composed of five hexagonal rings of circular air-holes with a larger hole diameter in the first inner ring. Numerical results show that a suitable designed W-type PCF could exhibit a loss peak on the confinement loss curve, which is different from the standard long wavelength cutoff property of the normal W-type fiber. The center wavelength and the magnitude of the confinement loss peak could be flexibly altered by varying the geometrical structure of the W-type PCF. The specially designed PCF could be of great interest for an in-line fiber filter or other applications.