Supercontinuum Gneneration and Modes Analysis in Secondary Cores of a Hollow-Core Photonic Crystal Fiber

We demonstrate the generation of supercontinuum spectra in three secondary cores of a hollow-core photonic crystal fiber pumped by femtosecond laser pulses, respectively. The supercontinuum spectra are mainly a result of the soliton self-frequency shift and an amplification of dispersive wave at visible wavelengths. Detailed mode simulations show that with the increasing core length, the modes transfer from "double-points" to "single-point" since the pump laser is more easily coupled into the two side cores of a secondary core when the core length is small. The simulation results also explain why the experimental observed far-field beam patterns of first two secondary cores are different.