Abstract

A current challenge is to have access to bright, few-cycle mid-IR laser pulses. However, a solution for compressing mid-IR high-energy laser pulses to few-cycle duration is currently under investigation. One promising possibility is filamentation-based soliton self-compression [1,2], but the energy scalability is still unknown. We here investigate a novel external compressor, see Fig. 1(a), originally proposed in [3] for the near-IR, and here show its promises for the mid-IR. It uses a quadratic nonlinear crystal cut for cascaded (strongly phase-mismatched) second-harmonic generation, where strong spectral broadening occurs through an effective self-defocusing nonlinearity. This cancels the crystal’s intrinsic self-focusing effect and prevents filamentation. A similar concept was proposed in the near-IR [4], but the advantage of the compressor proposed here is that the spectral broadening occurs in the anomalous dispersion range of the crystal, which creates a very linear, negative chirp across the spectrally broadened pulse. Thus, external compression with standard positive dispersion elements will result in highly efficient and high-quality compression with reduced compression pedestals.

© 2015 IEEE