Abstract
Advanced applications of attosecond pulses require the implementation of experimental techniques for a complete and accurate characterization of the pulse temporal characteristics. The method of choice is the frequency resolved optical gating for the complete reconstruction of attosecond bursts (FROG-CRAB), which requires the development of suitable reconstruction algorithms. In the last few years, various numerical techniques have been proposed and implemented, characterized by different levels of accuracy, robustness, and computational load. Many of them are based on the central momentum approximation (CMA), which may pose severe limits in the reconstruction accuracy. Alternative techniques have been successfully developed, based on the implementation of reconstruction algorithms which do not rely on this approximation, such as the Volkov-transform generalized projection algorithm (VTGPA). The main drawback is a notable increase of the computational load. We propose a new method, called refined iterative ptychographic engine (rePIE), which combines the advantages of a robust algorithm based on CMA, characterized by a fast convergence, with the accuracy of advanced algorithms not based on such approximation. The main idea is to perform a first fast iterative ptychographic engine (ePIE) reconstruction and then refine the result with just a few iterations of the VTGPA in order to correct for the error introduced by the CMA. We analyse the accuracy of the novel reconstruction method by comparing the residual error (i.e., the difference between the reconstructed and the simulated original spectrograms) when VTGPA, ePIE, and rePIE reconstructions are employed. We show that the rePIE approach is particularly useful in the case of short attosecond pulses characterized by a broad spectrum in the vacuum-ultraviolet (VUV)–extreme-ultraviolet (XUV) region.
Highlights
The capability to follow electronic and nuclear processes evolving on ultrafast time scales is essential to foster the comprehension of the physical and chemical properties of matter
We propose a new method, called refined iterative ptychographic engine, which combines the advantages of a robust algorithm based on central momentum approximation (CMA), characterized by a fast convergence, with the accuracy of advanced algorithms not based on such approximation
We showed that the CMA in FROG-CRAB reconstructions based on a ptychographic algorithm mainly affects the reconstructed IR femtosecond pulse
Summary
The capability to follow electronic and nuclear processes evolving on ultrafast time scales is essential to foster the comprehension of the physical and chemical properties of matter. Ultrashort light pulses proved to be a powerful tool to investigate such dynamics. As direct measurements with electronic devices are impossible in this time domain, one of the first priority tasks in attosecond science was to develop techniques capable to characterize the temporal properties of the attosecond pulses. Attosecond streaking [4,5], in combination with iterative algorithms for phase reconstruction, was established as a powerful and versatile tool suited for the purpose. The constant improvement of both theoretical models and experimental techniques has pushed the time resolution of attosecond experiments, driving the search for increasingly precise attosecond pulse reconstruction
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