Design for photonic crystal fibers with high nonlinearity and flattened dispersion for self-frequency shift of Raman soliton

A new concept of photonic crystal fiber（PCF） with high nonlinearity and flattened dispersion was designed. The PCF structure is indeed a hexagon lattice. The bigger air holes in the outer rings are used to confine the light field into the core region for enhancing the nonlinearity. The flattened dispersion can be achieved by adjusting the diameters of six smaller air holes in the first ring, and six micro air holes are inserted between smaller air holes for higher nonlinearity and the better flattened dispersion. By optimizing the size of the smaller and micro holes, the PCF can reach to high nonlinearity of 23.3 W-1·km^-1 and the low dispersion of 51.32 ps/（nm·km） with the fluctuation range of 0.98 ps/（nm·km）, which is within the wavelength range of 1 400 nm to 1 900 nm. The designed PCF can be used in important applications in realizing the Raman soliton self-frequency shift（RSSFS）.