Ultra-flattened dispersion and large mode area single-mode photonic crystal fiber

Abstract

A novel photonic crystal fiber with ultra-flattened dispersion and large mode area is demonstrated. All air holes are arranged in the section according to triangular regulation and with identical spacing. The thirteen air holes, which in the middle of the section arrayed in the shape of snowflake, are smaller than the other air holes in the outer cladding region, form the large core region of PCF. Because the effective refractive index of the core region is higher than the cladding region, total internal reflective (TIR) can occur in the interface between the core and cladding, and optical field can be located mainly within the region of snowflake form. Obviously, this kind of PCF has large mode area because the thirteen holes holding together increase the core area of PCF visibly. On the other hand, not only ultra-flattened dispersion character can be realized in a broadband wavelength range, but also the flattened dispersion curve can easily be shifted in parallel from negative to zero, even to positive when the air holes of the core region is changed while the air holes size of cladding and spacing in the whole section remain fixed. Desired dispersion character and modal area can be realized in our designed PCFs with special section structure by optimizing the match of the spacing and air hole size in core and cladding regions.