Limits to compression with cascaded quadratic soliton compressors

TL;DR

This paper investigates the physical limits of pulse compression using cascaded quadratic soliton compressors, highlighting the roles of group-velocity mismatch, nonlinearities, and dispersion in preventing ideal single-cycle pulse generation.

Contribution

It introduces a nonlocal model for cascaded quadratic soliton compressors and identifies key physical mechanisms that limit pulse compression, including GVM effects and higher-order dispersion.

Findings

Oscillatory nonlocal response inhibits compression in nonstationary regime

Single-cycle pulse compression is theoretically possible in certain conditions

Competing nonlinearities and dispersive waves ultimately prevent reaching single-cycle durations

Abstract

We study cascaded quadratic soliton compressors and address the physical mechanisms that limit the compression. A nonlocal model is derived, and the nonlocal response is shown to have an additional oscillatory component in the nonstationary regime when the group-velocity mismatch (GVM) is strong. This inhibits efficient compression. Raman-like perturbations from the cascaded nonlinearity, competing cubic nonlinearities, higher-order dispersion, and soliton energy may also limit compression, and through realistic numerical simulations we point out when each factor becomes important. We find that it is theoretically possible to reach the single-cycle regime by compressing high-energy fs pulses for wavelengths $\lambda=1.0-1.3 \mu{\rm m}$ in a $\beta$-barium-borate crystal, and it requires that the system is in the stationary regime, where the phase mismatch is large enough to overcome the detrimental GVM effects. However, the simulations show that reaching single-cycle duration is ultimately inhibited by competing cubic nonlinearities as well as dispersive waves, that only show up when taking higher-order dispersion into account.