科研之友
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摘要
Attosecond pulses have potential applications in the fields of physics, chemistry, biology, and medicine owing to the extremely high time resolution brought by their extremely short pulse widths. The generation and measurement technology of attosecond pulses provides a powerful means for the study of electron dynamical process in atoms. Since the date of its birth, the time width of an attosecond pulse has become shorter and shorter, making its measurement a challenging task. Although attosecond pulses are more and more widely used in the study of ultrafast dynamics and more interest is attracted into the field of attosecond science, it is undeniable that there are still difficulties and challenges for the measurement of attosecond pulses. This review is divided into two parts. The first part presents the development of technics for characterizing attosecond pulses, and briefly describes several experimental principles, setups and results for acquiring time-domain information of attosecond pulses, including RABITT (reconstruction of attosecond beating by interference of two-photon transitions) and laser-assisted lateral X-ray photoionization for measuring attosecond pulse train, attosecond streak camera for measuring single attosecond pulses, TIPTOE (tunneling ionization with a perturbation for the time-domain observation of an electric field) for measuring time-domain information of periodic pulses, as well as theoretical proposals such as attosecond cross correlation, asymmetric photoionization method, and SPIDER (attosecond spectral phase interferometry for direct electric-field reconstruction). The second part introduces the principle and structure of inversion algorithms for extracting time-domain information of attosecond pulses from spectrograms obtained with an attosecond streak camera, including FROG-CRAB (frequency resolved optical gating for complete reconstruction of attosecond bursts), PROOF (phase retrieval by omega oscillation filtering), VTGPA (Volkov transform generalized projections algorithm), PROBP-AC (phase retrieval of broadband pulses with autocorrelation) and CVGN (conditional variational generative network). We also evaluate the calculation time and accuracy of the algorithms. Finally, we summarize the experimental and theoretical challenges of the characterization of attosecond pulses, and look forward to the future development of attosecond pulse measurement.
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