Ultra-flattened chromatic dispersion and highly nonlinear photonic crystal fibers with ultralow confinement loss employing hybrid cladding

• Two novel photonic crystal fibers (PCFs) with hybrid cladding are proposed.
• Ultra-flattened dispersion can be achieved in the proposed PCFs.
• The nonlinear coefficients in both proposed PCFs are very high.
• Ultralow confinement loss of lower than 0.001 dB/km can be achieved in the PCFs.
• Our proposed DF-PCFs are robust to fabrication imperfections.

In this paper, two new types of dispersion-flattened photonic crystal fibers (DF-PCFs) with highly nonlinear and ultralow confinement loss are proposed. These new PCF structures adopt hybrid cladding with different air-holes diameters, pitches and air-holes arranged fashions. In order to analyze the proposed PCFs, the full-vector finite element method with anisotropic perfectly matched layers has been used. Results show that the ultra-flattened dispersion of 0.931 ps/(nm km) (DF-PCF1) and 1.533 ps/(nm km) (DF-PCF2) can be achieved in the wavelength range from 1.3 to 1.6 μm with confinement losses lower than 0.001 dB/km in the same wavelength range. Meanwhile, the nonlinear coefficients of our proposed PCFs are greater than 23.83 W−1 km−1 (DF-PCF1) and 29.65 W−1 km−1 (DF-PCF2) at the wavelength of 1.55 μm, and two near-zero dispersion values of 0.328 ps/(nm km) (DF-PCF1) and −0.015 ps/(nm km) (DF-PCF2) can also be obtained at the same wavelength. Furthermore, the influence of manufacturing imperfections of parameters on dispersion and nonlinearity is discussed to verify the robustness of our design.