Supercontinuum generation dynamics in highly nonlinear photonic crystal fiber with normal and anomalous dispersion

This study investigates ultrashort pulse propagation and supercontinuum (SC) generation in lead silicate photonic crystal fibers (PCFs) with near-zero normal and anomalous dispersion using the finite-difference time-domain (FDTD) method. A comparative analysis is performed using the split-step Fourier method for pump pulses of 20, 50, and 100 fs durations at 1550 nm with a peak power of 1 kW. The results demonstrate that a 20 fs pulse in the normal dispersion regime produces an SC spectrum spanning 800–2500 nm, achieving a broad and coherent output primarily driven by self-phase modulation and four-wave mixing. In contrast, an anomalous dispersion regime results in an SC spectrum extending from 1000 to 3000 nm, dominated by soliton fission and Raman-induced soliton self-frequency shift. The presence of two zero-dispersion wavelengths (1.2 and 1.9 μm) enhances dispersive wave generation, contributing to extended spectral broadening. The proposed PCF design ensures high nonlinearity \((\gamma ={415 \text{W}}^{-1}{\text{Km}}^{-1})\) and low confinement loss making it suitable for broadband SC generation at low input power. This study provides a promising approach for compact and efficient ultra-broadband light sources with applications in telecommunications, imaging, and optical sensing.