New publication in Phys. Rev. Applied: Long-lived refractive-index changes induced by femtosecond ionization in gas-filled single-ring photonic-crystal fibers
Plasma recombination always follows photoionization of gas by intense femtosecond laser pulses, causing refractive-index changes via thermal and hydrodynamic effects. In gas-filled hollow-core photonic crystal fibers, these phenomena are induced by self-compressing pulses with microjoule energies. Using spatially-resolved interferometric probing from the side of the fiber, we uncover refractive-index changes with tens-of-µs lifetimes and observe plasma-driven acoustic waves that excite megahertz vibrations in the microstructure of the fiber. Our results imply that temporal non-local interactions of successive pulses will become important in any gas-based laser system operating simultaneously at high intensities and repetition rates.