Abstract
High-field experiments are very sensitive to the exact value of the peak intensity of an optical pulse due to the nonlinearity of the underlying processes. Therefore, precise knowledge of the pulse intensity, which is mainly limited by the accuracy of the temporal characterization, is a key prerequisite for the correct interpretation of experimental data. While the detection of energy and spatial profile is well established, the unambiguous temporal characterization of intense optical pulses, another important parameter required for intensity evaluation, remains a challenge, especially at relativistic intensities and a few-cycle pulse duration. Here, we report on the progress in the temporal characterization of intense laser pulses and present the relativistic surface second harmonic generation dispersion scan (RSSHG-D-scan)—a new approach allowing direct on-target temporal characterization of high-energy, few-cycle optical pulses at relativistic intensity.
Highlights
Accurate knowledge of the on-target pulse intensity is essential for the correct interpretation of high-field experiments involving highly nonlinear processes
second harmonic generation (SHG) saturation intensity Saturation must be avoided in any measurement setup, including the RSSHG-dispersion scan (D-scan)
In a standard D-scan, SHG saturation needs to be avoided to ensure the quadratic scaling of the second harmonic signal with the intensity of the fundamental radiation, which allows for precise pulse reconstruction
Summary
Accurate knowledge of the on-target pulse intensity is essential for the correct interpretation of high-field experiments involving highly nonlinear processes. The on-target intensity can be estimated directly via different gas ionization processes, such as the intensity scaling of the above-threshold ionization[1,2], the yield of single or multiple charged ions[3,4], the photoelectron/photoion momentum distribution from ionization by circularly polarized laser fields[5] and similar These techniques are limited to intensities significantly below the relativistic limit (1:37 ́ 1018 W=cm[2] at a central wavelength of 1 μm) and require a precise theory of the ionization process as well as knowledge of the temporal and spatial pulse shape to achieve reasonable precision of the averaging of the electron/ion impact over the intensity distribution[5]. This image can be obtained with a combination of an HDR CCD camera and the additional extension of the dynamic range by the sequential measurement of unsaturated and saturated images with different attenuations
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