Design of a highly nonlinear twin bow-tie polymer photonic quasi-crystal fiber with high birefringence

• A PQF with high birefringence, high nonlinearity and low dispersion is presented.
• The twin bow-tie polymer-based PQF maintains single mode operation in 1.8–2.2 μm.
• The birefringence is 2.43 × 10−3 and the nonlinearity is 118 W−1 km−1 at 2 μm with the pitch of 3.3 μm.
• The influence of deviation within 2% of imperfections is discussed to verify the robustness.
• The PQF have important applications in four-wave mixing or super-continuum generation.

A twin bow-tie polymer-based photonic quasi-crystal fiber with high birefringence, high nonlinearity and low dispersion as well as maintaining single mode operation is presented in the wavelength range 1.8–2.2 μm. Through optimizing fiber structure parameter using a full-vector finite-element method combined with perfectly matched layers boundary condition, the birefringence is as high as 2.43 × 10−3, the nonlinearity is as high as 118 W−1 km−1, and the dispersion is only 25 ps/nm/km at 2 μm with the holes pitch of 3.3 μm. From the point of fabrication, the influences of deviation of each air hole diameter are discussed to verify the robustness of the photonic quasi-crystal fiber designed.