Scaling of self-compression of near-IR femtosecond pulses in hollow-core fibers down to the single-cycle limit

Abstract

We numerically investigate the scaling of self-compression processes with experimental parameters for near-infrared ultrashort pulses (30 fs) in gas-filled hollow-core fiber (HCF). These simulations over a wide-range of input pulse energies as well as filling gas pressures reveal a remarkable scaling of the self-compression process and dynamics. As a function of soliton order N, we identify the relation between the propagation distance after which self-compression in the HCF begins and the subsequent propagation length up to which the pulse remains maximally compressed; both these length scales decrease with an increase in N, the soliton order. Although previous investigations revealed pulse compression scaling laws which provide a good approximation for input pulse-widths ∼100 fs down to the limit where soliton fission begins to dominate the dynamics, these are not sufficiently accurate to describe the entire scaling dynamics. Instead, we identify a more generalized set of scaling laws by taking both third-order dispersion and the saturation of the compression factor due to soliton fission into account. These conclusions about scaling are robust: our simulations were carried out over a wide range of realistic input pulse energies and gas pressures as implemented in laboratories taking into account higher-order dispersive properties of the gaseous propagating medium. Therefore, given that these numerical investigations consider conditions typically applied in practice in laboratories, this work provides elegant design principles and guideposts relevant to realizing systems capable of achieving self-compression at substantially high pulse energies down to the few-cycle limit; they are of paramount importance in generating single as well as trains of attosecond pulses and acceleration strategies for electrons and ions in intense laser pulses.