Carrier-envelope phase stability of hollow-fibers used for high-energy, few-cycle pulse generation

TL;DR

This study examines the carrier-envelope phase stability of hollow fibers used for generating high-energy, few-cycle pulses, highlighting the effects of ionization and different pumping methods on CEP stability.

Contribution

It provides new insights into the CEP stability limits and effects of ionization and pumping techniques in hollow-fiber pulse generation systems.

Findings

Saturation of pulse energy at 0.6 mJ in static neon-filled fibers

Maximum pulse energy increased to 0.8 mJ with differential pumping or circular polarization

Ionization-induced CEP instability occurs at higher energies but does not worsen with gas flow

Abstract

We investigated the carrier-envelope phase (CEP) stability of a hollow-fiber setup used for high-energy, few-cycle pulse generation. Saturation of the output pulse energy is observed at 0.6 mJ for a 260 um inner-diameter, 1 m long fiber, statically filled with neon, with the pressure adjusted to achieve an output spectrum capable of supporting sub-4fs pulses. The maximum output pulse energy can be increased to 0.8mJ by using either differential pumping, or circularly polarized input pulses. We observe the onset of an ionization-induced CEP instability, which does not increase beyond an input pulse energy of 1.25 mJ due to losses in the fiber caused by ionization. There is no significant difference in the CEP stability with differential pumping compared to static-fill, demonstrating that gas flow in differentially pumped fibers does not degrade the CEP stabilization.