Demonstration of Single‐Shot Measurements of 1013 Ultrahigh‐Contrast Pulses by Manipulating Cross‐Correlation

In strong‐field physics experiments with high‐intensity lasers, single‐shot characterization of the temporal contrast between the laser pulse peak and its temporal pedestal is important; this allows fast optimization of the pulse contrast and meaningful comparison with theory for each pulse shot. To date, high contrast ratios of 1010 have been demonstrated in single‐shot measurements for petawatt (PW) lasers. However, ultrahigh contrast ratios of ≈1013, as required for the planned 200 PW lasers, pose challenges to high‐intensity laser technologies and have thus far remained open for investigation. This article reports a pilot demonstration of ultrahigh‐contrast measurements by adapting a single‐shot cross‐correlator (SSCC). An evaluation method for the SSCC detection limit is introduced. The strategy mimics the test beam with known spatial contrast, whose cross‐correlation is equivalent to that of a test pulse with ultrahigh temporal contrast. The ultimate contrast measurement limit of 1013 is achieved, which corresponds to the highest pulse intensity by optical damage and the lowest temporal pedestal by single‐photon detection. The photon noise of the detector is observed and becomes dominant as the temporal pedestal of the optical pulse decreases. The demonstrated detection ability is applied to a high‐contrast laser system, suggesting the accessibility of ultrahigh‐contrast measurements.