Theoretical study of dispersive wave generation in ar-filled hollow-core PCF above the plasma threshold

Hollow-core photonic-crystal fibre (HC-PCF) [1] provides a highly efficient means for investigating light-matter interactions at sustained intensity levels inaccessible to both traditional bulk setups (due to limited interaction lengths) or conventional optical fibres (due to the low damage threshold of glass). Recent experiments have shown that strong UV pulses can be generated, through emission of dispersive radiation, by launching near-IR femtosecond pulses into a gas-filled kagomé-lattice PCF [2]. Phase-matching to the UV can be accounted for through the special dispersion characteristics of the gas-filled HC-PCF [3]. Shorter UV wavelengths require higher energy pulses, causing the intensity to enter the ionisation regime when pulse propagation will be influenced by the presence of free electrons. The transition from the “traditional” regime where the Kerr effect dominates to the plasma regime where ionisation becomes important (novel in the context of photonic crystal fibres) is studied numerically in this work.