Fig. 1. Different technologies for measuring pulse duration time based on delay scan autocorrelation. (a) Experimental setup for second-order harmonic autocorrelation^[34]; (b) schematic of FROG algorithm^[39]; (c) single shot autocorrelation principle^[53]

Fig. 2. Different techniques of frequency-domain spectral interferometry with delay. (a) Schematic of spectral interference^[59]; (b) principle of SPIDER^[34]

Fig. 3. Phase parameter scan measurement technologies based on time-domain phase modulation. (a) Principle of MIIPS^[68]; (b) experimental setup for D-Scan^[70]

Fig. 4. Different technologies for two-dimensional space-time measurement of laser field. (a) Experimental setup for SEA-F-SPIDER^[91]; (b) experimental setup for SRSI-ETE^[92]; (c) principle of CROAK^[91]; (d) experimental setup for scanning SEA-TADPOLE^[97]

Fig. 5. Measurement of spatiotemporal characteristics of TW femtosecond laser pulses based on STRIPED-FISH technology^[103]. (a) Principle of STRIPED-FISH; (b) raw data of TW laser pulse measured by STRIPED-FISH, where the left image is spatial distribution of the intensity of each wavelength channel for reference laser, and the right image is interference field of each wavelength channel when the measured laser and the reference laser appear at the same time; (c) evolution of spatiotemporal distribution during the focused transmission of TW femtosecond laser pulses calculated with measured spatiotemporal distribution of laser pulses

Fig. 6. Spatiotemporal distribution measurement technology of femtosecond laser pulse based on Fourier transform spectroscopy. (a) Experimental setup and basic process of data processing of TERMITES^[113-114]; (b)(c) representative experimental results of spatiotemporal distribution measurement of femtosecond laser based on Fourier transform spectroscopy^[115], where image (b) is spatial distribution of different spectral components of laser pulse to be measured ( the middle row is spatial amplitude distribution and the bottom row is spatial phase distribution) and image (c) is spectral intensity and time-domain waveform of laser pulse to be measured at different spatial positions (reflects strong spatiotemporal coupling effect of the laser pulse)

Fig. 7. CASSI hyperspectral imaging technology^[126]. (a) Schematic of CASSI experimental setup; (b) two-dimensional original data measured by CASSI hyperspectral imaging technology; (c) spatial intensity distribution of each spectral component of the laser pulse by inversion algorithm, i.e. the hyperspectral images

Fig. 8. Block diagrams of multispectral imaging technology. (a) Principle of STAMP^[147]; (b) principle of FINOPA^[150]

Fig. 9. Principle of in-situ measurement of spatial structure information. Consider the change in the propagation direction of the XUV pulse caused by three atoms in the y direction. Perturbation light (purple) and driving light (red) are incident with an angle θ_p and delay τ. The atoms at＋y₀ and－y₀ correspond to different delays Δτ^＋ and Δτ^－. Compared with the XUV pulse wavefront (red) without perturbation, the pulse wavefront changes (purple) after adding perturbation light, causing the propagation direction to change by an angle of θ