On long-lived effects in gas-filled hollow-core fibers

Following interaction with light, media can exhibit long-lived changes in their optical properties that can affect the propagation of delayed radiation. These effects, which include thermal phenomena among others, have been observed and explored in a large variety of systems and platforms. In free-space filamentation, long-lived effects have been exploited for guiding high-intensity light, while in femtosecond enhancement cavities and fiber lasers, they introduce limits to the maximum power. Here, we investigate long-lived effects in gas-filled hollow-core fibers—a platform that is finding multiple applications in nonlinear optics and sensing, and where similar dynamics have been recently observed. We derive a model to describe how long-lived changes in the filling gas affect the profile and effective index of the waveguide, validate it through numerical simulation, and use it to explore the impact on the phase matching conditions of nonlinear processes.