Relativistic few-cycle pulses with high contrast from picosecond-pumped OPCPA

For experiments in plasma, nuclear, and high-energy physics, there is a strong demand for laser pulses exhibiting relativistic intensity, few-cycle pulse duration, and a very high contrast. Here we present a picosecond-pumped optical parametric chirped pulse amplification (OPCPA) system delivering pulses at 10 Hz repetition rate with the following key parameters: a compressed pulse duration of less than 7 fs (close to the Fourier limit), a contrast of better than 10(11) starting from 1 ps before the main pulse, and a peak intensity of 6.9 x 10(19) W/cm(2) achieved with an off-axis parabolic mirror (f/1.6). In a proof-of-principle experiment, these pulses were used to generate high harmonics from solid surfaces with photon energies exceeding 55 eV. These results underline the promising perspectives of the reported system for relativistic light-matter interaction experiments and attosecond science

Towards intense isolated attosecond pulses from relativistic surface high harmonics

Relativistic surface high harmonics have been considered a unique source for the generation of intense isolated attosecond pulses in the extreme ultra-violet and x-ray spectral ranges. Their practical realization, however, is still a challenging task and requires identification of optimum experimental conditions and parameters. Here, we present measurements and particle-in-cell simulations to determine the optimum values for the most important parameters. In particular, we investigate the dependence of harmonics efficiency, divergence, and beam quality on the pre-plasma scale length as well as identify the optimum conditions for generation of isolated attosecond pulses by measuring the dependence of the harmonics spectrum on the carrier - envelope phase of the driving infrared field. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen