Numerical simulation and experimental analysis of photonic band gap in hollow-core photonic crystal fibres

Based on the full-vector plane-wave method (FVPWM), a hollow-core photonic crystal fibre (HC-PCF) fabricated by using the improved stack-and-draw technique is simulated. Under given propagation constants beta, several effective photonic band gaps with different sizes emerge within the visible wavelength range from 575 to 720 nm. The fundamental mode and second-order mode lying in a part of PBGs are investigated. In the transmission spectrum tested, the positions of PBGs are discovered to be shifting to shorter wavelengths. The main reason is the existence of interstitial holes at nodes in the cladding region. In the later experiment, green light is observed propagating in the air-core region, and the result is more consistent with our theoretical simulation.