Highly nonlinear with low confinement losses square photonic crystal fiber based on a four-hole unit

• We report a novel PCF with low confinement loss and highly nonlinear coefficient.
• Increase the nonlinear coefficient by decreasing the core diameter.
• Increase the nonlinear coefficient by decreasing Λ.

A novel simple structure of a highly nonlinear square photonic crystal fiber with low confinement losses is proposed. The simulation results show that a nonlinear coefficient of 83.3 W−1 km−1 and a low confinement loss of less than 10−9 dB/m at the wavelength of 1.55 μm, and the corresponding effective mode area is about 1.46 μm2 by introducing the unique four-hole unit structure in the cladding region. The proposed PCF is expected to be useful for super-continuum generation, nonlinear optics and optical communication systems.