Demonstration of contrast improvement and spectral broadening in thin solid plates

Here we demonstrate that the pulses in thin solid plates (TSPs) can simultaneously realize contrast improvement and spectral broadening. In a proof-of-principle experiment, we used nine thin fused silica plates to make the beam form a series of foci in sequence, by which the divergence of the beam of the main pulse was seriously changed. After the last plate, the intense center spot of the output beam was picked out, and the energy of about 129 µJ was obtained for the 400 µJ input pulses, corresponding to a total transmission efficiency of more than 30%. The contrast measurement showed that the contrast was improved by 2 orders of magnitude. Meanwhile, the cleaned pulses were broadened spectrally, spanning from 680 to 930 nm at the -23dB intensity level and giving a compressed pulse of 11.3 fs. These characteristics make the TSP method suitable to generate broadband seed pulses for high-contrast, few-cycle intense lasers.