High birefringence and near‐zero dispersion control of nonlinear photonic crystal fibers with a double‐cladded coaxial core

Optical propagation characteristics of high birefringence (HB), near‐zero chromatic dispersion, and small effective mode area are first investigated along with simultaneously effective controllability for the new double‐cladded coaxial core photonic crystal fibers with the breakthrough air‐hole defects at the middle‐top, middle‐bottom, right‐top, and left‐bottom, as pairs, which enable the adaptation of novel systematic approach for design goals in the inner first hexagonal cladding layer. Compared with results (around 3.2 × 10−4) of well‐known HB optical fibers, superior performance for preserving the lightwave polarization state by about three times higher HB levels has been achieved with additive advantages of fabrication from only pure fused silica material and broadly unlimited stable single‐mode operation.