Design and Numerical Analysis of a Highly Nonlinear Dual-Core Photonic Crystal Fiber with Ultra-Low Confinement Loss at 1.55 µm Wavelength

Abstract In this paper, we propose and rigorously analyse a novel dual-core photonic crystal fibre (DC-PCF) design based on silica-air micro-structure. The fibre geometry is designed to reach a compromise between high optical nonlinearities and very low confinement loss at the standard telecommunication wavelength of \(\:\lambda\:=1.55\mu\:m\). Using the Full-Vector Finite Element Method (Full-Vector FEM) combined with circular Perfectly Matched Layers (PML), the fundamental propagation parameters—including modal field distributions, effective refractive index \(\:{(n}_{eff)}\), effective mode area ( \(\:{A}_{eff})\), nonlinear coefficient (\(\:\gamma\:)\), supermode coupling characteristics, and confinement loss—are investigated. Numerical convergence tests confirm that for the optimized ratio \(\:\raisebox{1ex}{$d$}\!\left/\:\!\raisebox{-1ex}{$\varLambda\:$}\right.\) = 0.76, the proposed DC-PCF yields a high nonlinear coefficient of 60 \(\:{W}^{-1}{Km}^{-1},\) atight effective mode area of 2.34\(\:{\mu\:m}^{2}\), and an ultra-low confinement loss of 0.001\(\:\raisebox{1ex}{$dB$}\!\left/\:\!\raisebox{-1ex}{$Km$}\right.\) at 1.55\(\:\mu\:m\). A comprehensive quantitative comparison with existing literature demonstrates the distinct numerical performance and potential suitability of this fiber for optical signal processing and future optical communication networks.