D-shape photonic crystal fiber for optical coherence tomography: design and analysis

A simple D-shaped photonic crystal fiber (D-PCF) with silicon-nano-crystal enrichment is proposed, with substantial nonlinearity, ultrahigh birefringence, and a higher degree of transverse resolution. To scrutinize the optical properties of the suggested D-PCF, the full vector finite-element method has been employed with an anisotropic perfect matched layer added around the designed model as a boundary condition. An elliptical air hole is being used as the core region of this simple structure, and thus it can achieve the most desirable property birefringence in the order of ^{10 − 2}. Tight mode confinement inside the core region benefits the large Kerr nonlinearity (γ) of 2.8 × 10⁵ and 2.3 × 10⁵ W ^{− 1} km ^{− 1} for X and Y polarization modes, respectively, at a wavelength of λ = 1.55 μm. Meanwhile, the numerical aperture is extraordinarily high, exceeding 0.60, with many applications in optical coherence tomography and other related fields. Due to the simple design and low air filling fraction, the D-PCF is feasible for practical realizations in many sectors.