Simultaneous ultra-intense pulses at petawatt laser facilities enable a broad range of experiments in nuclear photonics and strong field quantum electrodynamics. These experiments often require very precise control of the time delays between pulses. We report measurements of the time delay between the two 1 PW outputs of the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility in Romania. The short-term standard deviation of the time delay was approximately half of the pulse duration of 23 fs, and the average delay drifted with up to 100 fs/h. The drift and sporadic delay jumps were corrected using a feedback loop, which reduced the long-term standard deviation of the delay close to its short-term value. These results imply that in ELI-NP experiments using two simultaneous pulses, a temporal overlap of better than half of the pulse duration can be achieved for more than two thirds of the shots, which would enable high data rate experiments using simultaneous petawatt pulses.

With ultrafast laser systems reaching presently 10 PW peak power or operating at high repetition rates, research towards ensuring the long-term, trouble-free performance of all laser-exposed optical components is critical. Our work is focused on providing insight into the optical material behavior at fluences below the standardized laser-induced damage threshold (LIDT) value by implementing a simultaneous dual analysis of surface emitted particles using a Langmuir probe (LP) and the target current (TC). ${\mathrm{HfO}}_2$ and ${\mathrm{ZrO}}_2$ thin films deposited on fused silica substrates by pulsed laser deposition at various ${\mathrm{O}}_2$ pressures for defect and stoichiometry control were irradiated by Gaussian, ultrashort laser pulses (800 nm, 10 Hz, 70 fs) in a wide range of fluences. Both TC and LP collected signals were in good agreement with the existing theoretical description of laser–matter interaction at an ultrashort time scale. Our approach for an in situ LIDT monitoring system provides measurable signals for below-threshold irradiation conditions that indicate the endurance limit of the optical surfaces in the single-shot energy scanning mode. The LIDT value extracted from the LP-TC system is in line with the multipulse statistical analysis done with ISO 21254-2:2011(E). The implementation of the LP and TC as on-shot diagnostic tools for optical components will have a significant impact on the reliability of next-generation ultrafast and high-power laser systems.