Photoionization-induced emission of tunable few-cycle mid-IR dispersive waves in gas-filled hollow-core photonic crystal fiber

摘要

We propose a scheme for the emission of few-cycle dispersive waves in themid-infrared using hollow-core photonic crystal fibers filled with noble gas.The underlying mechanism is the formation of a plasma cloud by aself-compressed, sub-cycle pump pulse. The resulting free-electron populationmodifies the fiber dispersion, allowing phase-matched access to dispersivewaves at otherwise inaccessible frequencies, well into the mid-IR. Remarkably,the pulses generated turn out to have durations of the order of two opticalcycles. In addition, this ultrafast emission, which occurs even in the absenceof a zero dispersion point between pump and mid-IR wavelengths, is tunable overa wide frequency range simply by adjusting the gas pressure. These theoreticalresults pave the way to a new generation of compact, fiber-based sources offew-cycle mid-IR radiation.